code: def _GetMessageFileKeys(self, event_log_provider_key):
      
      table_names = ['message_file_per_event_log_provider']
      column_names = ['message_file_key']
      condition = 'event_log_provider_key == {0:d}'.format(
          event_log_provider_key)
  
      generator = self._database_file.GetValues(
          table_names, column_names, condition)
      for values in generator:
        yield values['message_file_key']
docs: Retrieves the message file keys.
  
      Args:
        event_log_provider_key (int): Event Log provider key.
  
      Yields:
        int: message file key.