chore: blacken (#772)

diff --git a/googleapiclient/discovery_cache/base.py b/googleapiclient/discovery_cache/base.py
index 00e466d..fbe4459 100644
--- a/googleapiclient/discovery_cache/base.py
+++ b/googleapiclient/discovery_cache/base.py
@@ -18,12 +18,13 @@
 
 
 class Cache(object):
-  """A base abstract cache class."""
-  __metaclass__ = abc.ABCMeta
+    """A base abstract cache class."""
 
-  @abc.abstractmethod
-  def get(self, url):
-    """Gets the content from the memcache with a given key.
+    __metaclass__ = abc.ABCMeta
+
+    @abc.abstractmethod
+    def get(self, url):
+        """Gets the content from the memcache with a given key.
 
     Args:
       url: string, the key for the cache.
@@ -32,14 +33,14 @@
       object, the value in the cache for the given key, or None if the key is
       not in the cache.
     """
-    raise NotImplementedError()
+        raise NotImplementedError()
 
-  @abc.abstractmethod
-  def set(self, url, content):
-    """Sets the given key and content in the cache.
+    @abc.abstractmethod
+    def set(self, url, content):
+        """Sets the given key and content in the cache.
 
     Args:
       url: string, the key for the cache.
       content: string, the discovery document.
     """
-    raise NotImplementedError()
+        raise NotImplementedError()