code: def is_file(dirname):
      '''Checks if a path is an actual file that exists'''
      if not os.path.isfile(dirname):
          msg = "{0} is not an existing file".format(dirname)
          raise argparse.ArgumentTypeError(msg)
      else:
          return dirnamf is_file(dirname):
      '''Checks if a path is an actual file that exists'''
      if not os.path.isfile(dirname):
          msg = "{0} is not an existing file".format(dirname)
          raise argparse.ArgumentTypeError(msg)
      else:
          return dirname
docs: Checks if a path is an actual file that exists