Mistake in output_dir and overwrite parameters validation

[Aivean]

This assert only lets in the following combination of parameter values:

• output_dir must exist and overwrite=False

onnx-pytorch/onnx_pytorch/code_gen.py

Lines 317 to 319 in 2902b4d

	assert os.path.exists(
	output_dir
	) and overwrite is not True, f"{output_dir} is not empty and overwrite is not True."

From the context is seems that other combinations of parameter values should also be valid, such as:

• output_dir doesn't exist an overwrite is whatever
• output_dir exist and overwrite=True

I think the fix is to change the clause to:

assert not os.path.exists(
     output_dir 
 ) or overwrite, f"{output_dir} is not empty and overwrite is not True." 

[fumihwh]

@Aivean Sorry for late reply.
Some PR will resolve this issue.