code: def read_user_documents_for_single_user_generator(user_twitter_id, mongo_database):
      
      collection_name = str(user_twitter_id)
      collection = mongo_database[collection_name]
      cursor = collection.find()
  
      for twitter_list in cursor:
          yield twitter_list
docs: Stores Twitter list objects that a Twitter user is a member of in different mongo collections.
  
      Inputs: - user_twitter_id: A Twitter user id.
              - mongo_database: A mongo database.
  
      Yields: - twitter_list: A tuple containing: * A Twitter user id.
                                                  * A python list containing Twitter lists in dictionary (json) format.