error when transform from har to py using command line

[rationalxde]

Getting below error when doing the transform

.......
File "C:\Users\mxu\workspace\nftenv\nftenv\Lib\site-packages\transformer\request.py", line 46, in
@DataClass
^^^^^^^^^
File "C:\Users\mxu\AppData\Local\Programs\Python\Python311\Lib\dataclasses.py", line 1220, in dataclass
return wrap(cls)
^^^^^^^^^
File "C:\Users\mxu\AppData\Local\Programs\Python\Python311\Lib\dataclasses.py", line 1210, in wrap
return _process_class(cls, init, repr, eq, order, unsafe_hash,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\mxu\AppData\Local\Programs\Python\Python311\Lib\dataclasses.py", line 958, in _process_class
cls_fields.append(_get_field(cls, name, type, kw_only))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\mxu\AppData\Local\Programs\Python\Python311\Lib\dataclasses.py", line 815, in _get_field
raise ValueError(f'mutable default {type(f.default)} for field '
ValueError: mutable default <class 'mappingproxy'> for field headers is not allowed: use default_factory

command line: transformer C:\Users\mxu\workspace\nftenv\har\ >locustfile.py

windows 10 64bit.

[rationalxde]

I downloaded the example har file www.google.com.har, and got the same error.