new_contents: from argparse import ArgumentParser
  from typing import Any, List, Optional
  
  from fragment_capping.molecule_for_fragment import cap_fragment, Fragment
  
  def parse_args():
      parser = ArgumentParser()
  
      parser.add_argument('--fragment', type=Fragment, help='')
  
      return parser.parse_args()
  
  if __name__ == '__main__':
      args = parse_args()
      print(
          cap_fragment(args.fragment),
      )
  
subject: Add an interface for cap_fragment()