code: def _IncludeFields(encoded_message, message, include_fields):
      
      if include_fields is None:
          return encoded_message
      result = json.loads(encoded_message)
      for field_name in include_fields:
          try:
              value = _GetField(message, field_name.split('.'))
              nullvalue = None
              if isinstance(value, list):
                  nullvalue = []
          except KeyError:
              raise exceptions.InvalidDataError(
                  'No field named %s in message of type %s' % (
                      field_name, type(message)))
          _SetField(result, field_name.split('.'), nullvalue)
      return json.dumps(result)
docs: Add the requested fields to the encoded message.