def ref_for_message_type(self, message_type):
name = self.__normalized_name(message_type)<EOL>if name not in self.__schemas:<EOL><INDENT>raise KeyError('<STR_LIT>', name)<EOL><DEDENT>return name<EOL>
Returns the JSON Schema id for the given message.

        Args:
          message_type: protorpc.message.Message class to be parsed.

        Returns:
          string, The JSON Schema id.

        Raises:
          KeyError: if the message hasn't been parsed via add_message().