code: def _get_cropped_file_names(self):
          
          files = [ff.name for ff in self.files]
          prefix = commonprefix(files)
          suffix = commonprefix([f[::-1] for f in files])[::-1]
          cropped = [f[len(prefix):-len(suffix)] for f in files]
          return cropped
docs: self.files with common path prefix/suffix removed