Registers the decorated method as the composer of a format.

        :param type: The unique name of the format
        :param meta: The extra information associated with the format

def composer(self, type, **meta):
        """Registers the decorated method as the composer of a format.

        :param type: The unique name of the format
        :param meta: The extra information associated with the format
        """
        def decorator(f):
            self.register_composer(type, f)
            if meta:
                self.register_meta(type, **meta)
            return f
        return decorator