docs: def main(args=None):
      """Start application."""
      parser = _parser()
  
      # Python 2 will error 'too few arguments' if no subcommand is supplied.
      # No such error occurs in Python 3, which makes it feasible to check
      # whether a subcommand was provided (displaying a help message if not).
      # argparse internals vary significantly over the major versions, so it's
      # much easier to just override the args passed to it. In this case, print
      # the usage message if there are no args.
      if args is None and len(sys.argv) <= 1:
          sys.argv.append('--help')
  
      options = parser.parse_args(args)
  
      # pass options to subcommand
      options.func(options)
  
      return 0