See: https://core.telegram.org/bots/api#addstickertoset

def addStickerToSet(self, user_id, name, png_sticker, emojis,
                        mask_position=None):
        """
        See: https://core.telegram.org/bots/api#addstickertoset
        """
        p = _strip(locals(), more=['png_sticker'])
        return self._api_request_with_file('addStickerToSet', _rectify(p), 'png_sticker', png_sticker)