old_contents: """
  Common MongoDB connection functions.
  """
  import pymongo
  from mongodb_proxy import MongoProxy
  
  
  # pylint: disable=bad-continuation
  def connect_to_mongodb(
      db, host,
      port=27017, tz_aware=True, user=None, password=None,
      retry_wait_time=0.1, proxy=True, **kwargs
  ):
      """
      Returns a MongoDB Database connection, optionally wrapped in a proxy. The proxy
      handles AutoReconnect errors by retrying read operations, since these exceptions
      typically indicate a temporary step-down condition for MongoDB.
      """
      # The MongoReplicaSetClient class is deprecated in Mongo 3.x, in favor of using
      # the MongoClient class for all connections. Update/simplify this code when using
      # PyMongo 3.x.
      if kwargs.get('replicaSet'):
          # Enable reading from secondary nodes in the MongoDB replicaset by using the
          # MongoReplicaSetClient class.
          # The 'replicaSet' parameter in kwargs is required for secondary reads.
          # The read_preference should be set to a proper value, like SECONDARY_PREFERRED.
          mongo_client_class = pymongo.MongoReplicaSetClient
      else:
          # No 'replicaSet' in kwargs - so no secondary reads.
          mongo_client_class = pymongo.MongoClient
  
      mongo_conn = pymongo.database.Database(
          mongo_client_class(
              host=host,
              port=port,
              tz_aware=tz_aware,
              document_class=dict,
              **kwargs
          ),
          db
      )
  
      if proxy:
          mongo_conn = MongoProxy(
              mongo_conn,
              wait_time=retry_wait_time
          )
  
      # If credentials were provided, authenticate the user.
      auth_src = None
      if kwargs.get('authSource'):
          auth_src=kwargs.get('authSource')
      if user is not None and password is not None:
          mongo_conn.authenticate(user, password, source=auth_src)
  
      return mongo_conn
  
new_contents: """
  Common MongoDB connection functions.
  """
  import pymongo
  from mongodb_proxy import MongoProxy
  
  
  # pylint: disable=bad-continuation
  def connect_to_mongodb(
      db, host,
      port=27017, tz_aware=True, user=None, password=None,
      retry_wait_time=0.1, proxy=True, **kwargs
  ):
      """
      Returns a MongoDB Database connection, optionally wrapped in a proxy. The proxy
      handles AutoReconnect errors by retrying read operations, since these exceptions
      typically indicate a temporary step-down condition for MongoDB.
      """
      # The MongoReplicaSetClient class is deprecated in Mongo 3.x, in favor of using
      # the MongoClient class for all connections. Update/simplify this code when using
      # PyMongo 3.x.
      if kwargs.get('replicaSet'):
          # Enable reading from secondary nodes in the MongoDB replicaset by using the
          # MongoReplicaSetClient class.
          # The 'replicaSet' parameter in kwargs is required for secondary reads.
          # The read_preference should be set to a proper value, like SECONDARY_PREFERRED.
          mongo_client_class = pymongo.MongoReplicaSetClient
      else:
          # No 'replicaSet' in kwargs - so no secondary reads.
          mongo_client_class = pymongo.MongoClient
  
      mongo_conn = pymongo.database.Database(
          mongo_client_class(
              host=host,
              port=port,
              tz_aware=tz_aware,
              document_class=dict,
              **kwargs
          ),
          db
      )
  
      if proxy:
          mongo_conn = MongoProxy(
              mongo_conn,
              wait_time=retry_wait_time
          )
  
      # If credentials were provided, authenticate the user.
      auth_src = kwargs.get('authSource')
  
      if user is not None and password is not None:
          mongo_conn.authenticate(user, password, source=auth_src)
  
      return mongo_conn
  
subject: optimize code in mongo connection function