human
Here's a good function header given the following:
I wrote the below code

    def MergeFromString(self, serialized):
        length = len(serialized)
        try:
            if (self._InternalParse(serialized, 0, length) != length):
                raise message_mod.DecodeError('Unexpected    end-group    tag.')
        except IndexError:
            raise message_mod.DecodeError('Truncated    message.')
        except struct.error as e:
            raise message_mod.DecodeError(e)
        return length
    cls.MergeFromString = MergeFromString
    local_ReadTag = decoder.ReadTag
    local_SkipField = decoder.SkipField
    decoders_by_tag = cls._decoders_by_tag
    def InternalParse(self, buffer, pos, end):
        self._Modified()
        field_dict = self._fields
        unknown_field_list = self._unknown_fields
        while (pos != end):
            (tag_bytes, new_pos) = local_ReadTag(buffer, pos)
            field_decoder = decoders_by_tag.get(tag_bytes)
            if (field_decoder is None):
                value_start_pos = new_pos
                new_pos = local_SkipField(buffer, new_pos, end, tag_bytes)
                if (new_pos == (-1)):
                    return pos
                if (not unknown_field_list):
                    unknown_field_list = self._unknown_fields = []
                unknown_field_list.append((tag_bytes, buffer[value_start_pos:new_pos]))
                pos = new_pos
            else:
                pos = field_decoder(buffer, new_pos, end, self, field_dict)
        return pos
    cls._InternalParse = InternalParse

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

def _AddMergeFromStringMethod(message_descriptor, cls):