def filename_to_list(filename):
 if isinstance(filename, (str, bytes)):
  return [filename]
 elif isinstance(filename, list):
  return filename
 elif is_container(filename):
  return [x for x in filename]
 else:
  return None

def filename_to_list ( filename ) : if isinstance ( filename , ( str , bytes ) ) : return [ filename ] elif isinstance ( filename , list ) : return filename elif is_container ( filename ) : return [ x for x in filename ] else : return None
returns a list given either a string or a list .