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

def send_photo(self, chat_id, photo, caption=None, reply_to_message_id=None, reply_markup=None):
        """
            Use this method to send photos. On success, the sent Message is returned.
        """
        self.logger.info('send photo %s', photo)
        payload = dict(chat_id=chat_id,
                       caption=caption,
                       reply_to_message_id=reply_to_message_id,
                       reply_markup=reply_markup)
        files = dict(photo=open(photo, 'rb'))
        return Message.from_api(self, **self._post('sendPhoto', payload, files))