docs: def add_argparser(self, root, parents):
          """
          Add arguments for this command.
          """
          parser = root.add_parser('diff', parents=parents)
          parser.set_defaults(func=self)
  
          parser.add_argument(
              '--secrets',
              dest='secrets', action='store',
              help='Path to the authorization secrets file (client_secrets.json).'
          )
  
          parser.add_argument(
              '-d', '--data',
              dest='data_path', action='store', default=None,
              help='Path to a existing JSON diff file.'
          )
  
          parser.add_argument(
             'report_a_path',
              action='store',
              help='Path to a JSON file containing the initial report data.'
          )
  
          parser.add_argument(
             'report_b_path',
              action='store',
              help='Path to a JSON file containing the report data to compare.'
          )
  
          parser.add_argument(
              'output_path',
              action='store',
              help='Path to output either an HTML report or a JSON data file.'
          )
  
          return parser