code: def get_default_database(self):
          
          warnings.warn("get_default_database is deprecated. Use get_database "
                        "instead.", DeprecationWarning, stacklevel=2)
          if self.__default_database_name is None:
              raise ConfigurationError('No default database defined')
  
          return self[self.__default_database_name]
docs: DEPRECATED - Get the database named in the MongoDB connection URI.
  
          >>> uri = 'mongodb://host/my_database'
          >>> client = MongoClient(uri)
          >>> db = client.get_default_database()
          >>> assert db.name == 'my_database'
          >>> db = client.get_database()
          >>> assert db.name == 'my_database'
  
          Useful in scripts where you want to choose which database to use
          based only on the URI in a configuration file.
  
          .. versionchanged:: 3.5
             Deprecated, use :meth:`get_database` instead.