code: def start(parser, argv, scope):
      
      args = parser.parse_args(argv)
  
      if not args.command:
          parser.print_help()
          raise SystemExit()
  
      # look up in the current scope for a function called 'run_<command>'
      # replacing all the dashes '-' with the lowercase character '_'
      func = scope.get('run_' + args.command.replace('-', '_'))
  
      # if no command has been found, raise a `NotImplementedError`
      if not func:
          raise NotImplementedError('Command `{}` not yet implemented'.
                                    format(args.command))
  
      args.multiprocess = getattr(args, 'multiprocess', False)
  
      if args.multiprocess is False:
          args.multiprocess = 1
      elif args.multiprocess is None:
          args.multiprocess = mp.cpu_count()
  
      return func(args)
docs: Utility function to execute a subcommand.
  
      The function will look up in the ``scope``
      if there is a function called ``run_<parser.args.command>``
      and will run it using ``parser.args`` as first positional argument.
  
      Args:
          parser: an ArgumentParser instance.
          argv: the list of command line arguments without the script name.
          scope (dict): map containing (eventually) the functions to be called.
  
      Raises:
          NotImplementedError: if ``scope`` doesn't contain a function called
                               ``run_<parser.args.command>``.