AttributeError: 'DummyFile' object has no attribute 'flush'

[dlevitas]

Describe the bug The following error occurs [in python] when attempting to use is_pet.pet_folder() on a folder containing DICOM-to-NIfTI transformed PET data:

To Reproduce

1. code/command used (copy/paste what you did)

   from pathlib import Path
   is_pet.pet_folder(Path(path/to/PET_NIFTI/folder))

2. error happening? (copy/paste the error)

   Traceback (most recent call last):
   File "./find_petdir.py", line 25, in <module>
   print([str(folder) for folder in is_pet.pet_folder(Path(root).resolve())])
   File "/usr/local/lib/python3.8/dist-packages/pypet2bids/is_pet.py", line 158, in pet_folder
   files = read_files_in_parallel(all_files, pet_file, n_jobs=1, return_only_path=True)
   File "/usr/local/lib/python3.8/dist-packages/pypet2bids/is_pet.py", line 61, in read_files_in_parallel
   results = Parallel(n_jobs=n_jobs)(delayed(function)(file_path, **kwargs) for file_path in file_paths)
   File "/usr/local/lib/python3.8/dist-packages/joblib/parallel.py", line 1863, in __call__
   return output if self.return_generator else list(output)
   File "/usr/local/lib/python3.8/dist-packages/joblib/parallel.py", line 1792, in _get_sequential_output
   res = func(*args, **kwargs)
   File "/usr/local/lib/python3.8/dist-packages/pypet2bids/is_pet.py", line 126, in pet_file
   read_file = spread_sheet_check_for_pet(file_path)
   File "/usr/local/lib/python3.8/dist-packages/pypet2bids/is_pet.py", line 26, in spread_sheet_check_for_pet
   data = helper_functions.open_meta_data(sourcefile)
   File "/usr/local/lib/python3.8/dist-packages/pypet2bids/helper_functions.py", line 406, in open_meta_data
   metadata_dataframe = use_me_to_read(metadata_path, sep=separator)
   TypeError: 'NoneType' object is not callable
   Exception ignored in: <pypet2bids.is_pet.DummyFile object at 0x7ff53daedf70>
   AttributeError: 'DummyFile' object has no attribute 'flush'

Expected behaviour I was anticipating ispet to return the folder path. At the very least, this seems a bit restrictive, as using ispet on the individual PET NIfTI file itself doesn't produce an error, it simply returns nothing. Perhaps this is the expected behavior, but it would be nice if ispet could determine that the file is indeed PET, simply transformed to the NIfTi format.

Desktop (please complete the following information):

• Linux OS pypet2bids version 1.2.10 (python)

[bendhouseart]

Seems to error out when tsv files are present.