cras_utils: Fix pylint errors and blank lines

Fix the blank lines and some pylint errors.

BUG=None
TEST=run pylint on cras_utils.py

Change-Id: I8a39b234fe9a508d86fe788a683d19e805e66fe7
Reviewed-on: https://chromium-review.googlesource.com/257943
Reviewed-by: Kalin Stoyanov <kalin@chromium.org>
Commit-Queue: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
diff --git a/client/cros/audio/cras_utils.py b/client/cros/audio/cras_utils.py
index e53e11d..0f4b801 100644
--- a/client/cros/audio/cras_utils.py
+++ b/client/cros/audio/cras_utils.py
@@ -2,10 +2,11 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+"""This module provides cras audio utilities."""
+
 import logging
 import re
 
-from autotest_lib.client.bin import utils
 from autotest_lib.client.cros.audio import cmd_utils
 
 _CRAS_TEST_CLIENT = '/usr/bin/cras_test_client'
@@ -17,10 +18,12 @@
     """A helper function to execute the playback_cmd."""
     cmd_utils.execute(playback_cmd(*args, **kargs))
 
+
 def capture(*args, **kargs):
     """A helper function to execute the capture_cmd."""
     cmd_utils.execute(capture_cmd(*args, **kargs))
 
+
 def playback_cmd(playback_file, block_size=None, duration=None,
                  channels=2, rate=48000):
     """Gets a command to playback a file with given settings.
@@ -30,6 +33,7 @@
     @param block_size: the number of frames per callback(dictates latency).
     @param duration: seconds to playback
     @param rate: the sampling rate
+
     """
     args = [_CRAS_TEST_CLIENT]
     args += ['--playback_file', playback_file]
@@ -41,6 +45,7 @@
     args += ['--rate', str(rate)]
     return args
 
+
 def capture_cmd(
         capture_file, block_size=None, duration=10, channels=1, rate=48000):
     """Gets a command to capture the audio into the file with given settings.
@@ -51,6 +56,7 @@
                      and command will keep capturing audio until it is
                      terminated.
     @param rate: the sampling rate.
+
     """
     args = [_CRAS_TEST_CLIENT]
     args += ['--capture_file', capture_file]
@@ -75,6 +81,7 @@
     @param channels: The number of channels of the recorded audio.
     @param duration: seconds to record.
     @param rate: the sampling rate.
+
     """
     args = [_CRAS_TEST_CLIENT]
     args += ['--loopback_file', output_file]
@@ -88,34 +95,42 @@
     """Set the system volume.
 
     @param volume: the system output vlume to be set(0 - 100).
+
     """
     args = [_CRAS_TEST_CLIENT]
     args += ['--volume', str(volume)]
     cmd_utils.execute(args)
 
+
 def set_node_volume(node_id, volume):
     """Set the volume of the given output node.
 
     @param node_id: the id of the output node to be set the volume.
     @param volume: the volume to be set(0-100).
+
     """
     args = [_CRAS_TEST_CLIENT]
     args += ['--set_node_volume', '%s:%d' % (node_id, volume)]
     cmd_utils.execute(args)
 
+
 def set_capture_gain(gain):
     """Set the system capture gain.
+
     @param gain the capture gain in db*100 (100 = 1dB)
+
     """
     args = [_CRAS_TEST_CLIENT]
     args += ['--capture_gain', str(gain)]
     cmd_utils.execute(args)
 
+
 def dump_server_info():
     """Gets the CRAS's server information."""
     args = [_CRAS_TEST_CLIENT, '--dump_server_info']
     return cmd_utils.execute(args, stdout=cmd_utils.PIPE)
 
+
 def get_selected_nodes():
     """Returns the pair of active output node and input node."""
     server_info = dump_server_info()
@@ -132,6 +147,7 @@
     """Sets the selected output node volume.
 
     @param volume: the volume to be set (0-100).
+
     """
     selected_output_node_id, _ = get_selected_nodes()
     set_node_volume(selected_output_node_id, volume)
@@ -143,7 +159,7 @@
     match = _RE_NUM_ACTIVE_STREAM.search(server_info)
     if not match:
         logging.error(server_info)
-        raise RuntimeException('Cannot find matched pattern')
+        raise RuntimeError('Cannot find matched pattern')
     return int(match.group(1))
 
 
@@ -151,6 +167,7 @@
     """Sets the system mute switch.
 
     @param is_mute: Set True to mute the system playback.
+
     """
     args = [_CRAS_TEST_CLIENT, '--mute', '1' if is_mute else '0']
     cmd_utils.execute(args)
@@ -160,6 +177,7 @@
     """Sets the capture mute switch.
 
     @param is_mute: Set True to mute the capture.
+
     """
     args = [_CRAS_TEST_CLIENT, '--capture_mute', '1' if is_mute else '0']
     cmd_utils.execute(args)
@@ -188,6 +206,7 @@
     @returns: True if there is any node of node_type plugged. False otherwise.
 
     @raises: ValueError: if cras server info format is not as expected.
+
     """
     # The label line
     # ID   Vol   Plugged  L/R swapped Time      Type       Name