联接路径：TypeError：join（）参数必须为str或字节，而不是'NoneType'

Question

@staticmethod
def get_abs_filename(filename):
    speak_result = os.path.abspath(os.path.join(os.path.dirname(__file__), 
                                   os.pardir, filename))
    return speak_result

有人可以告诉我我做错了什么吗？

File "D:\Luan Van\Jennie\Jennie\TextManager\speaker.py", line 37, in get_abs_filename
    os.pardir, filename))
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python36\lib\ntpath.py", line 115, 
    in joingenericpath._check_arg_types('join', path, *paths)
  File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python36\lib\genericpath.py", line 149,
    in _check_arg_types(funcname, s.__class__.__name__)) from None
TypeError: join() argument must be str or bytes, not 'NoneType'