human
I wrote the below code

    def ListFields(self):
        all_fields = [item for item in self._fields.iteritems() if _IsPresent(item)]
        all_fields.sort(key=(lambda item: item[0].number))
        return all_fields
    cls.ListFields = ListFields

What's a good function header?
assistant
#Here's a good function header.

def _AddListFieldsMethod(message_descriptor, cls):