code: def add_message(self, message_type):
      
      name = self.__normalized_name(message_type)
      if name not in self.__schemas:
        # Set a placeholder to prevent infinite recursion.
        self.__schemas[name] = None
        schema = self.__message_to_schema(message_type)
        self.__schemas[name] = schema
      return name
docs: Add a new message.
  
      Args:
        message_type: protorpc.message.Message class to be parsed.
  
      Returns:
        string, The JSON Schema id.
  
      Raises:
        KeyError if the Schema id for this message_type would collide with the
        Schema id of a different message_type that was already added.