docs: def invoked(self, ctx):
          """
          Guacamole method used by the command ingredient.
  
          :param ctx:
              The guacamole context object. Context provides access to all
              features of guacamole. The argparse ingredient adds the ``args``
              attribute to it. That attribute contains the result of parsing
              command line arguments.
          :returns:
              The return code of the command. Guacamole translates ``None`` to a
              successful exit status (return code zero).
          """
          print("{} + {} = {}".format(
              ctx.args.x,
              ctx.args.y,
              ctx.args.x + ctx.args.y))