apiclient/discovery.py

# Copyright (C) 2010 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Client for discovery based APIs

A client library for Google's discovery based APIs.
"""

__author__ = 'jcgregorio@google.com (Joe Gregorio)'
__all__ = [
    'build',
    'build_from_document'
    'fix_method_name',
    'key2param'
    ]

import copy
import httplib2
import logging
import os
import re
import uritemplate
import urllib
import urlparse
import mimeparse
import mimetypes

try:
  from urlparse import parse_qsl
except ImportError:
  from cgi import parse_qsl

from apiclient.errors import HttpError
from apiclient.errors import InvalidJsonError
from apiclient.errors import MediaUploadSizeError
from apiclient.errors import UnacceptableMimeTypeError
from apiclient.errors import UnknownApiNameOrVersion
from apiclient.errors import UnknownFileType
from apiclient.http import HttpRequest
from apiclient.http import MediaFileUpload
from apiclient.http import MediaUpload
from apiclient.model import JsonModel
from apiclient.model import MediaModel
from apiclient.model import RawModel
from apiclient.schema import Schemas
from email.mime.multipart import MIMEMultipart
from email.mime.nonmultipart import MIMENonMultipart
from oauth2client.util import positional
from oauth2client.anyjson import simplejson

logger = logging.getLogger(__name__)

URITEMPLATE = re.compile('{[^}]*}')
VARNAME = re.compile('[a-zA-Z0-9_-]+')
DISCOVERY_URI = ('https://www.googleapis.com/discovery/v1/apis/'
  '{api}/{apiVersion}/rest')
DEFAULT_METHOD_DOC = 'A description of how to use this function'

# Parameters accepted by the stack, but not visible via discovery.
STACK_QUERY_PARAMETERS = ['trace', 'pp', 'userip', 'strict']

# Python reserved words.
RESERVED_WORDS = ['and', 'assert', 'break', 'class', 'continue', 'def', 'del',
                  'elif', 'else', 'except', 'exec', 'finally', 'for', 'from',
                  'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or',
                  'pass', 'print', 'raise', 'return', 'try', 'while', 'body']


def fix_method_name(name):
  """Fix method names to avoid reserved word conflicts.

  Args:
    name: string, method name.

  Returns:
    The name with a '_' prefixed if the name is a reserved word.
  """
  if name in RESERVED_WORDS:
    return name + '_'
  else:
    return name


def _add_query_parameter(url, name, value):
  """Adds a query parameter to a url.

  Replaces the current value if it already exists in the URL.

  Args:
    url: string, url to add the query parameter to.
    name: string, query parameter name.
    value: string, query parameter value.

  Returns:
    Updated query parameter. Does not update the url if value is None.
  """
  if value is None:
    return url
  else:
    parsed = list(urlparse.urlparse(url))
    q = dict(parse_qsl(parsed[4]))
    q[name] = value
    parsed[4] = urllib.urlencode(q)
    return urlparse.urlunparse(parsed)


def key2param(key):
  """Converts key names into parameter names.

  For example, converting "max-results" -> "max_results"

  Args:
    key: string, the method key name.

  Returns:
    A safe method name based on the key name.
  """
  result = []
  key = list(key)
  if not key[0].isalpha():
    result.append('x')
  for c in key:
    if c.isalnum():
      result.append(c)
    else:
      result.append('_')

  return ''.join(result)


@positional(2)
def build(serviceName,
          version,
          http=None,
          discoveryServiceUrl=DISCOVERY_URI,
          developerKey=None,
          model=None,
          requestBuilder=HttpRequest):
  """Construct a Resource for interacting with an API.

  Construct a Resource object for interacting with an API. The serviceName and
  version are the names from the Discovery service.

  Args:
    serviceName: string, name of the service.
    version: string, the version of the service.
    http: httplib2.Http, An instance of httplib2.Http or something that acts
      like it that HTTP requests will be made through.
    discoveryServiceUrl: string, a URI Template that points to the location of
      the discovery service. It should have two parameters {api} and
      {apiVersion} that when filled in produce an absolute URI to the discovery
      document for that service.
    developerKey: string, key obtained from
      https://code.google.com/apis/console.
    model: apiclient.Model, converts to and from the wire format.
    requestBuilder: apiclient.http.HttpRequest, encapsulator for an HTTP
      request.

  Returns:
    A Resource object with methods for interacting with the service.
  """
  params = {
      'api': serviceName,
      'apiVersion': version
      }

  if http is None:
    http = httplib2.Http()

  requested_url = uritemplate.expand(discoveryServiceUrl, params)

  # REMOTE_ADDR is defined by the CGI spec [RFC3875] as the environment
  # variable that contains the network address of the client sending the
  # request. If it exists then add that to the request for the discovery
  # document to avoid exceeding the quota on discovery requests.
  if 'REMOTE_ADDR' in os.environ:
    requested_url = _add_query_parameter(requested_url, 'userIp',
                                         os.environ['REMOTE_ADDR'])
  logger.info('URL being requested: %s' % requested_url)

  resp, content = http.request(requested_url)

  if resp.status == 404:
    raise UnknownApiNameOrVersion("name: %s  version: %s" % (serviceName,
                                                            version))
  if resp.status >= 400:
    raise HttpError(resp, content, uri=requested_url)

  try:
    service = simplejson.loads(content)
  except ValueError, e:
    logger.error('Failed to parse as JSON: ' + content)
    raise InvalidJsonError()

  return build_from_document(content, base=discoveryServiceUrl, http=http,
      developerKey=developerKey, model=model, requestBuilder=requestBuilder)


@positional(1)
def build_from_document(
    service,
    base=None,
    future=None,
    http=None,
    developerKey=None,
    model=None,
    requestBuilder=HttpRequest):
  """Create a Resource for interacting with an API.

  Same as `build()`, but constructs the Resource object from a discovery
  document that is it given, as opposed to retrieving one over HTTP.

  Args:
    service: string, discovery document.
    base: string, base URI for all HTTP requests, usually the discovery URI.
      This parameter is no longer used as rootUrl and servicePath are included
      within the discovery document. (deprecated)
    future: string, discovery document with future capabilities (deprecated).
    http: httplib2.Http, An instance of httplib2.Http or something that acts
      like it that HTTP requests will be made through.
    developerKey: string, Key for controlling API usage, generated
      from the API Console.
    model: Model class instance that serializes and de-serializes requests and
      responses.
    requestBuilder: Takes an http request and packages it up to be executed.

  Returns:
    A Resource object with methods for interacting with the service.
  """

  # future is no longer used.
  future = {}

  service = simplejson.loads(service)
  base = urlparse.urljoin(service['rootUrl'], service['servicePath'])
  schema = Schemas(service)

  if model is None:
    features = service.get('features', [])
    model = JsonModel('dataWrapper' in features)
  return Resource(http=http, baseUrl=base, model=model,
                  developerKey=developerKey, requestBuilder=requestBuilder,
                  resourceDesc=service, rootDesc=service, schema=schema)


def _cast(value, schema_type):
  """Convert value to a string based on JSON Schema type.

  See http://tools.ietf.org/html/draft-zyp-json-schema-03 for more details on
  JSON Schema.

  Args:
    value: any, the value to convert
    schema_type: string, the type that value should be interpreted as

  Returns:
    A string representation of 'value' based on the schema_type.
  """
  if schema_type == 'string':
    if type(value) == type('') or type(value) == type(u''):
      return value
    else:
      return str(value)
  elif schema_type == 'integer':
    return str(int(value))
  elif schema_type == 'number':
    return str(float(value))
  elif schema_type == 'boolean':
    return str(bool(value)).lower()
  else:
    if type(value) == type('') or type(value) == type(u''):
      return value
    else:
      return str(value)


MULTIPLIERS = {
    "KB": 2 ** 10,
    "MB": 2 ** 20,
    "GB": 2 ** 30,
    "TB": 2 ** 40,
    }


def _media_size_to_long(maxSize):
  """Convert a string media size, such as 10GB or 3TB into an integer.

  Args:
    maxSize: string, size as a string, such as 2MB or 7GB.

  Returns:
    The size as an integer value.
  """
  if len(maxSize) < 2:
    return 0
  units = maxSize[-2:].upper()
  multiplier = MULTIPLIERS.get(units, 0)
  if multiplier:
    return int(maxSize[:-2]) * multiplier
  else:
    return int(maxSize)


def createMethod(methodName, methodDesc, rootDesc, schema):
  """Creates a method for attaching to a Resource.

  Args:
    methodName: string, name of the method to use.
    methodDesc: object, fragment of deserialized discovery document that
      describes the method.
    rootDesc: object, the entire deserialized discovery document.
    schema: object, mapping of schema names to schema descriptions.
  """
  methodName = fix_method_name(methodName)
  pathUrl = methodDesc['path']
  httpMethod = methodDesc['httpMethod']
  methodId = methodDesc['id']

  mediaPathUrl = None
  accept = []
  maxSize = 0
  if 'mediaUpload' in methodDesc:
    mediaUpload = methodDesc['mediaUpload']
    mediaPathUrl = (rootDesc['rootUrl'] + 'upload/' + rootDesc['servicePath']
                    + pathUrl)
    accept = mediaUpload['accept']
    maxSize = _media_size_to_long(mediaUpload.get('maxSize', ''))

  if 'parameters' not in methodDesc:
    methodDesc['parameters'] = {}

  # Add in the parameters common to all methods.
  for name, desc in rootDesc.get('parameters', {}).iteritems():
    methodDesc['parameters'][name] = desc

  # Add in undocumented query parameters.
  for name in STACK_QUERY_PARAMETERS:
    methodDesc['parameters'][name] = {
        'type': 'string',
        'location': 'query'
        }

  if httpMethod in ['PUT', 'POST', 'PATCH'] and 'request' in methodDesc:
    methodDesc['parameters']['body'] = {
        'description': 'The request body.',
        'type': 'object',
        'required': True,
        }
    if 'request' in methodDesc:
      methodDesc['parameters']['body'].update(methodDesc['request'])
    else:
      methodDesc['parameters']['body']['type'] = 'object'
  if 'mediaUpload' in methodDesc:
    methodDesc['parameters']['media_body'] = {
        'description':
          'The filename of the media request body, or an instance of a '
          'MediaUpload object.',
        'type': 'string',
        'required': False,
        }
    if 'body' in methodDesc['parameters']:
      methodDesc['parameters']['body']['required'] = False

  argmap = {} # Map from method parameter name to query parameter name
  required_params = [] # Required parameters
  repeated_params = [] # Repeated parameters
  pattern_params = {}  # Parameters that must match a regex
  query_params = [] # Parameters that will be used in the query string
  path_params = {} # Parameters that will be used in the base URL
  param_type = {} # The type of the parameter
  enum_params = {} # Allowable enumeration values for each parameter

  if 'parameters' in methodDesc:
    for arg, desc in methodDesc['parameters'].iteritems():
      param = key2param(arg)
      argmap[param] = arg

      if desc.get('pattern', ''):
        pattern_params[param] = desc['pattern']
      if desc.get('enum', ''):
        enum_params[param] = desc['enum']
      if desc.get('required', False):
        required_params.append(param)
      if desc.get('repeated', False):
        repeated_params.append(param)
      if desc.get('location') == 'query':
        query_params.append(param)
      if desc.get('location') == 'path':
        path_params[param] = param
      param_type[param] = desc.get('type', 'string')

  for match in URITEMPLATE.finditer(pathUrl):
    for namematch in VARNAME.finditer(match.group(0)):
      name = key2param(namematch.group(0))
      path_params[name] = name
      if name in query_params:
        query_params.remove(name)

  def method(self, **kwargs):
    # Don't bother with doc string, it will be over-written by createMethod.

    for name in kwargs.iterkeys():
      if name not in argmap:
        raise TypeError('Got an unexpected keyword argument "%s"' % name)

    # Remove args that have a value of None.
    keys = kwargs.keys()
    for name in keys:
      if kwargs[name] is None:
        del kwargs[name]

    for name in required_params:
      if name not in kwargs:
        raise TypeError('Missing required parameter "%s"' % name)

    for name, regex in pattern_params.iteritems():
      if name in kwargs:
        if isinstance(kwargs[name], basestring):
          pvalues = [kwargs[name]]
        else:
          pvalues = kwargs[name]
        for pvalue in pvalues:
          if re.match(regex, pvalue) is None:
            raise TypeError(
                'Parameter "%s" value "%s" does not match the pattern "%s"' %
                (name, pvalue, regex))

    for name, enums in enum_params.iteritems():
      if name in kwargs:
        # We need to handle the case of a repeated enum
        # name differently, since we want to handle both
        # arg='value' and arg=['value1', 'value2']
        if (name in repeated_params and
            not isinstance(kwargs[name], basestring)):
          values = kwargs[name]
        else:
          values = [kwargs[name]]
        for value in values:
          if value not in enums:
            raise TypeError(
                'Parameter "%s" value "%s" is not an allowed value in "%s"' %
                (name, value, str(enums)))

    actual_query_params = {}
    actual_path_params = {}
    for key, value in kwargs.iteritems():
      to_type = param_type.get(key, 'string')
      # For repeated parameters we cast each member of the list.
      if key in repeated_params and type(value) == type([]):
        cast_value = [_cast(x, to_type) for x in value]
      else:
        cast_value = _cast(value, to_type)
      if key in query_params:
        actual_query_params[argmap[key]] = cast_value
      if key in path_params:
        actual_path_params[argmap[key]] = cast_value
    body_value = kwargs.get('body', None)
    media_filename = kwargs.get('media_body', None)

    if self._developerKey:
      actual_query_params['key'] = self._developerKey

    model = self._model
    if methodName.endswith('_media'):
      model = MediaModel()
    elif 'response' not in methodDesc:
      model = RawModel()

    headers = {}
    headers, params, query, body = model.request(headers,
        actual_path_params, actual_query_params, body_value)

    expanded_url = uritemplate.expand(pathUrl, params)
    url = urlparse.urljoin(self._baseUrl, expanded_url + query)

    resumable = None
    multipart_boundary = ''

    if media_filename:
      # Ensure we end up with a valid MediaUpload object.
      if isinstance(media_filename, basestring):
        (media_mime_type, encoding) = mimetypes.guess_type(media_filename)
        if media_mime_type is None:
          raise UnknownFileType(media_filename)
        if not mimeparse.best_match([media_mime_type], ','.join(accept)):
          raise UnacceptableMimeTypeError(media_mime_type)
        media_upload = MediaFileUpload(media_filename,
                                       mimetype=media_mime_type)
      elif isinstance(media_filename, MediaUpload):
        media_upload = media_filename
      else:
        raise TypeError('media_filename must be str or MediaUpload.')

      # Check the maxSize
      if maxSize > 0 and media_upload.size() > maxSize:
        raise MediaUploadSizeError("Media larger than: %s" % maxSize)

      # Use the media path uri for media uploads
      expanded_url = uritemplate.expand(mediaPathUrl, params)
      url = urlparse.urljoin(self._baseUrl, expanded_url + query)
      if media_upload.resumable():
        url = _add_query_parameter(url, 'uploadType', 'resumable')

      if media_upload.resumable():
        # This is all we need to do for resumable, if the body exists it gets
        # sent in the first request, otherwise an empty body is sent.
        resumable = media_upload
      else:
        # A non-resumable upload
        if body is None:
          # This is a simple media upload
          headers['content-type'] = media_upload.mimetype()
          body = media_upload.getbytes(0, media_upload.size())
          url = _add_query_parameter(url, 'uploadType', 'media')
        else:
          # This is a multipart/related upload.
          msgRoot = MIMEMultipart('related')
          # msgRoot should not write out it's own headers
          setattr(msgRoot, '_write_headers', lambda self: None)

          # attach the body as one part
          msg = MIMENonMultipart(*headers['content-type'].split('/'))
          msg.set_payload(body)
          msgRoot.attach(msg)

          # attach the media as the second part
          msg = MIMENonMultipart(*media_upload.mimetype().split('/'))
          msg['Content-Transfer-Encoding'] = 'binary'

          payload = media_upload.getbytes(0, media_upload.size())
          msg.set_payload(payload)
          msgRoot.attach(msg)
          body = msgRoot.as_string()

          multipart_boundary = msgRoot.get_boundary()
          headers['content-type'] = ('multipart/related; '
                                     'boundary="%s"') % multipart_boundary
          url = _add_query_parameter(url, 'uploadType', 'multipart')

    logger.info('URL being requested: %s' % url)
    return self._requestBuilder(self._http,
                                model.response,
                                url,
                                method=httpMethod,
                                body=body,
                                headers=headers,
                                methodId=methodId,
                                resumable=resumable)

  docs = [methodDesc.get('description', DEFAULT_METHOD_DOC), '\n\n']
  if len(argmap) > 0:
    docs.append('Args:\n')

  # Skip undocumented params and params common to all methods.
  skip_parameters = rootDesc.get('parameters', {}).keys()
  skip_parameters.extend(STACK_QUERY_PARAMETERS)

  all_args = argmap.keys()
  args_ordered = [key2param(s) for s in methodDesc.get('parameterOrder', [])]

  # Move body to the front of the line.
  if 'body' in all_args:
    args_ordered.append('body')

  for name in all_args:
    if name not in args_ordered:
      args_ordered.append(name)

  for arg in args_ordered:
    if arg in skip_parameters:
      continue

    repeated = ''
    if arg in repeated_params:
      repeated = ' (repeated)'
    required = ''
    if arg in required_params:
      required = ' (required)'
    paramdesc = methodDesc['parameters'][argmap[arg]]
    paramdoc = paramdesc.get('description', 'A parameter')
    if '$ref' in paramdesc:
      docs.append(
          ('  %s: object, %s%s%s\n    The object takes the'
          ' form of:\n\n%s\n\n') % (arg, paramdoc, required, repeated,
            schema.prettyPrintByName(paramdesc['$ref'])))
    else:
      paramtype = paramdesc.get('type', 'string')
      docs.append('  %s: %s, %s%s%s\n' % (arg, paramtype, paramdoc, required,
                                          repeated))
    enum = paramdesc.get('enum', [])
    enumDesc = paramdesc.get('enumDescriptions', [])
    if enum and enumDesc:
      docs.append('    Allowed values\n')
      for (name, desc) in zip(enum, enumDesc):
        docs.append('      %s - %s\n' % (name, desc))
  if 'response' in methodDesc:
    if methodName.endswith('_media'):
      docs.append('\nReturns:\n  The media object as a string.\n\n    ')
    else:
      docs.append('\nReturns:\n  An object of the form:\n\n    ')
      docs.append(schema.prettyPrintSchema(methodDesc['response']))

  setattr(method, '__doc__', ''.join(docs))
  return (methodName, method)


def createNextMethod(methodName):
  """Creates any _next methods for attaching to a Resource.

  The _next methods allow for easy iteration through list() responses.

  Args:
    methodName: string, name of the method to use.
  """
  methodName = fix_method_name(methodName)

  def methodNext(self, previous_request, previous_response):
    """Retrieves the next page of results.

Args:
  previous_request: The request for the previous page. (required)
  previous_response: The response from the request for the previous page. (required)

Returns:
  A request object that you can call 'execute()' on to request the next
  page. Returns None if there are no more items in the collection.
    """
    # Retrieve nextPageToken from previous_response
    # Use as pageToken in previous_request to create new request.

    if 'nextPageToken' not in previous_response:
      return None

    request = copy.copy(previous_request)

    pageToken = previous_response['nextPageToken']
    parsed = list(urlparse.urlparse(request.uri))
    q = parse_qsl(parsed[4])

    # Find and remove old 'pageToken' value from URI
    newq = [(key, value) for (key, value) in q if key != 'pageToken']
    newq.append(('pageToken', pageToken))
    parsed[4] = urllib.urlencode(newq)
    uri = urlparse.urlunparse(parsed)

    request.uri = uri

    logger.info('URL being requested: %s' % uri)

    return request

  return (methodName, methodNext)


class Resource(object):
  """A class for interacting with a resource."""

  def __init__(self, http, baseUrl, model, requestBuilder, developerKey,
               resourceDesc, rootDesc, schema):
    """Build a Resource from the API description.

    Args:
      http: httplib2.Http, Object to make http requests with.
      baseUrl: string, base URL for the API. All requests are relative to this
          URI.
      model: apiclient.Model, converts to and from the wire format.
      requestBuilder: class or callable that instantiates an
          apiclient.HttpRequest object.
      developerKey: string, key obtained from
          https://code.google.com/apis/console
      resourceDesc: object, section of deserialized discovery document that
          describes a resource. Note that the top level discovery document
          is considered a resource.
      rootDesc: object, the entire deserialized discovery document.
      schema: object, mapping of schema names to schema descriptions.
    """
    self._dynamic_attrs = []

    self._http = http
    self._baseUrl = baseUrl
    self._model = model
    self._developerKey = developerKey
    self._requestBuilder = requestBuilder
    self._resourceDesc = resourceDesc
    self._rootDesc = rootDesc
    self._schema = schema

    self._set_service_methods()

  def _set_dynamic_attr(self, attr_name, value):
    """Sets an instance attribute and tracks it in a list of dynamic attributes.

    Args:
      attr_name: string; The name of the attribute to be set
      value: The value being set on the object and tracked in the dynamic cache.
    """
    self._dynamic_attrs.append(attr_name)
    self.__dict__[attr_name] = value

  def __getstate__(self):
    """Trim the state down to something that can be pickled.

    Uses the fact that the instance variable _dynamic_attrs holds attrs that
    will be wiped and restored on pickle serialization.
    """
    state_dict = copy.copy(self.__dict__)
    for dynamic_attr in self._dynamic_attrs:
      del state_dict[dynamic_attr]
    del state_dict['_dynamic_attrs']
    return state_dict

  def __setstate__(self, state):
    """Reconstitute the state of the object from being pickled.

    Uses the fact that the instance variable _dynamic_attrs holds attrs that
    will be wiped and restored on pickle serialization.
    """
    self.__dict__.update(state)
    self._dynamic_attrs = []
    self._set_service_methods()

  def _set_service_methods(self):
    self._add_basic_methods(self._resourceDesc, self._rootDesc, self._schema)
    self._add_nested_resources(self._resourceDesc, self._rootDesc, self._schema)
    self._add_next_methods(self._resourceDesc, self._schema)

  def _add_basic_methods(self, resourceDesc, rootDesc, schema):
    # Add basic methods to Resource
    if 'methods' in resourceDesc:
      for methodName, methodDesc in resourceDesc['methods'].iteritems():
        fixedMethodName, method = createMethod(
            methodName, methodDesc, rootDesc, schema)
        self._set_dynamic_attr(fixedMethodName,
                               method.__get__(self, self.__class__))
        # Add in _media methods. The functionality of the attached method will
        # change when it sees that the method name ends in _media.
        if methodDesc.get('supportsMediaDownload', False):
          fixedMethodName, method = createMethod(
              methodName + '_media', methodDesc, rootDesc, schema)
          self._set_dynamic_attr(fixedMethodName,
                                 method.__get__(self, self.__class__))

  def _add_nested_resources(self, resourceDesc, rootDesc, schema):
    # Add in nested resources
    if 'resources' in resourceDesc:

      def createResourceMethod(methodName, methodDesc):
        """Create a method on the Resource to access a nested Resource.

        Args:
          methodName: string, name of the method to use.
          methodDesc: object, fragment of deserialized discovery document that
            describes the method.
        """
        methodName = fix_method_name(methodName)

        def methodResource(self):
          return Resource(http=self._http, baseUrl=self._baseUrl,
                          model=self._model, developerKey=self._developerKey,
                          requestBuilder=self._requestBuilder,
                          resourceDesc=methodDesc, rootDesc=rootDesc,
                          schema=schema)

        setattr(methodResource, '__doc__', 'A collection resource.')
        setattr(methodResource, '__is_resource__', True)

        return (methodName, methodResource)

      for methodName, methodDesc in resourceDesc['resources'].iteritems():
        fixedMethodName, method = createResourceMethod(methodName, methodDesc)
        self._set_dynamic_attr(fixedMethodName,
                               method.__get__(self, self.__class__))

  def _add_next_methods(self, resourceDesc, schema):
    # Add _next() methods
    # Look for response bodies in schema that contain nextPageToken, and methods
    # that take a pageToken parameter.
    if 'methods' in resourceDesc:
      for methodName, methodDesc in resourceDesc['methods'].iteritems():
        if 'response' in methodDesc:
          responseSchema = methodDesc['response']
          if '$ref' in responseSchema:
            responseSchema = schema.get(responseSchema['$ref'])
          hasNextPageToken = 'nextPageToken' in responseSchema.get('properties',
                                                                   {})
          hasPageToken = 'pageToken' in methodDesc.get('parameters', {})
          if hasNextPageToken and hasPageToken:
            fixedMethodName, method = createNextMethod(methodName + '_next')
            self._set_dynamic_attr(fixedMethodName,
                                   method.__get__(self, self.__class__))