UnboundLocalError: local variable 'keypoints' referenced before assignment

Traceback (most recent call last):
  File "inference.py", line 345, in <module>
    main()
  File "inference.py", line 82, in main
    lm = kp_extractor.extract_keypoint(frames_pil, './temp/'+base_name+'_landmarks.txt')
  File "D:\video-retalking\third_part\face3d\extract_kp_videos.py", line 29, in extract_keypoint
    current_kp = self.extract_keypoint(image)
  File "D:\video-retalking\third_part\face3d\extract_kp_videos.py", line 57, in extract_keypoint
    return keypoints
UnboundLocalError: local variable 'keypoints' referenced before assignment