km_regional_fits_to_tsv
=============================================

.. py:function:: petpal.utils.image_io.km_regional_fits_to_tsv(fit_results_dir: str, out_tsv_dir: str)

   Tidies the output of regional kinetic modeling results by converting JSON files into a TSV file
   with one row per fit region. Accomodates lists by converting them into key-value pairs. Assigns
   a subject and session to each row inferred from the original TAC file path.

   Requires fields to be identical across all JSON results files.

   :param fit_results_dir: Directory where RTM results are stored in JSON files.
   :type fit_results_dir: str
   :param out_tsv_dir: Path where resulting TSV file containing fit results will be stored.
   :type out_tsv_dir: str

   :returns: *km_fits (pd.DataFrame)* -- DataFrame containing KM fit data for all regions.