code: def send_audio(self, chat_id, audio, duration=None, performer=None, title=None, reply_to_message_id=None, reply_markup=None):
          
          self.logger.info('sending audio payload %s', audio)
          payload = dict(chat_id=chat_id,
                         duration=duration,
                         performer=performer,
                         title=title,
                         reply_to_message_id=reply_to_message_id,
                         reply_markup=reply_markup)
          files = dict(audio=open(audio, 'rb'))
          return Message.from_api(self, **self._post('sendAudio', payload, files))
docs: Use this method to send audio files, if you want Telegram clients to display them in the music player.
              Your audio must be in the .mp3 format. On success, the sent Message is returned. Bots can currently send
              audio files of up to 50 MB in size, this limit may be changed in the future.
  
              For backward compatibility, when the fields title and performer are both empty and the mime-type of the
              file to be sent is not audio/mpeg, the file will be sent as a playable voice message. For this to work,
              the audio must be in an .ogg file encoded with OPUS.
  
              This behavior will be phased out in the future.
              For sending voice messages, use the send_voice method instead.