Unable to answer call (dev-branch)

[SolntsevLA]

I'm using dev-branch and code

from pyVoIP.SIP.message.message import SIPMessage
from pyVoIP.credentials import CredentialsManager
from pyVoIP.VoIP.call import VoIPCall,CallState
from pyVoIP.VoIP.error import InvalidStateError
from pyVoIP.VoIP.phone import VoIPPhone, VoIPPhoneParameter



import time
import wave
import traceback
import librosa
import soundfile


class Call(VoIPCall):
    def ringing(self, invite_request):
        return custom_answer(self)



    def bye(self):
        print('Bye')
        return self.bye()


def custom_answer(call):
    print('start answering')
    original_data, sr = librosa.load('x00_autogen_sample_music.wav', sr=44100)
    resampled_data = librosa.resample(original_data, orig_sr=sr, target_sr=8000)
    soundfile.write('to_play.wav',resampled_data,samplerate=8000,subtype='PCM_U8')
    f = wave.open('to_play.wav', 'rb')
    frames = f.getnframes()
    data = f.readframes(frames)
    f.close()
    return call.answer()
    #call.write_audio(data)

    # call.answer()
    # call.write_audio(data)
    # d=10
    # while d>0:
    #     print(call.state)
    #     time.sleep(.1)



if __name__ == "__main__":




  cm = CredentialsManager()
  server_username='---'
  server_password='---'

  cm.add(server_username, server_password)

  server_ip='----'
  server_port=5060
  server_user='5264'
  bind_ip='---'
  params = VoIPPhoneParameter(server_ip, server_port, server_user, credentials_manager=cm, bind_ip=bind_ip,call_class=Call)
  phone = VoIPPhone(params)
  phone.start()
  print(phone.get_status())


  # call_x=phone.call('89200126698')
  # while call_x.state!=CallState.ENDED:
  #     time.sleep(1)
  #     if call_x.state==CallState.ANSWERED:
  #         original_data, sr = librosa.load('x00_autogen_sample_music.wav', sr=44100)
  #         resampled_data = librosa.resample(original_data, orig_sr=sr, target_sr=8000)
  #         soundfile.write('to_send.wav',resampled_data,samplerate=8000,subtype='PCM_U8')
  #         f = wave.open('to_send.wav', 'rb',)
  #         frames = f.getnframes()
  #         print(f.getframerate())
  #         data = f.readframes(frames)
  #         f.close()
  #         call_x.write_audio(data)



  #print(call_x.state)
  input('Press enter to disable the phone\n')
  phone.stop()

Output is

PhoneStatus.REGISTERED
Press enter to disable the phone
sys:1: UserWarning: RTP Payload type G729 not found.
sys:1: UserWarning: RTP Payload type G729 not found.
sys:1: UserWarning: RTP Payload type speex not found.
sys:1: UserWarning: RTP Payload type iLBC not found.
sys:1: UserWarning: RTP Payload type iLBC not found.
sys:1: UserWarning: RTP Payload type G729 not found.
sys:1: UserWarning: RTP Payload type AMR not found.
start answering

It seems, that ringing () function works and then is happends nothing