Use this method to send .webp stickers. On success, the sent Message is returned.

def send_sticker(self, chat_id=None, sticker=None, reply_to_message_id=None, reply_markup=None):
        """
            Use this method to send .webp stickers. On success, the sent Message is returned.
        """
        payload = dict(chat_id=chat_id,
                       reply_to_message_id=reply_to_message_id,
                       reply_markup=reply_markup)
        files = dict(sticker=open(sticker, 'rb'))
        return Message.from_api(api, **self._post('sendSticker', payload, files))