docs: def get_sorted_series_files(self, startpath="", series_number=None, return_files_with_info=False,
                                  sort_keys="SliceLocation", return_files=True, remove_doubled_slice_locations=True):
          """
          Function returns sorted list of dicom files. File paths are organized
          by SeriesUID, StudyUID and FrameUID
  
  
          :param startpath: path prefix. E.g. "~/data"
          :param series_number: ID of series used for filtering the data
          :param return_files_with_info: return more complex information about sorted files
          :param return_files: return simple list of sorted files
          :type sort_keys: One key or list of keys used for sorting method by the order of keys.
  
          """
          dcmdir = self.files_with_info[:]
  
          # select sublist with SeriesNumber
          if series_number is not None:
              dcmdir = [
                  line for line in dcmdir if line['SeriesNumber'] == series_number
              ]
          dcmdir = sort_list_of_dicts(dcmdir, keys=sort_keys)
  
          logger.debug('SeriesNumber: ' + str(series_number))
  
          if remove_doubled_slice_locations:
              dcmdir = self._remove_doubled_slice_locations(dcmdir)
  
          filelist = []
          for onefile in dcmdir:
              filelist.append(os.path.join(startpath,
                                           self.dirpath, onefile['filename']))
              # head, tail = os.path.split(onefile['filename'])
  
  
          retval = []
          if return_files:
              retval.append(filelist)
          if return_files_with_info:
              retval.append(dcmdir)
  
          if len(retval) == 0:
              retval = None
          elif len(retval) == 1:
              retval = retval[0]
          else:
              retval = tuple(retval)
  
          return retval