code: def execute(path, argv=None, environ=None, command_class=ExternalSearchCommand):
      
      assert issubclass(command_class, ExternalSearchCommand)
      command_class(path, argv, environ).execute()
docs: :param path:
      :type path: basestring
      :param argv:
      :type: argv: list, tuple, or None
      :param environ:
      :type environ: dict
      :param command_class: External search command class to instantiate and execute.
      :type command_class: type
      :return:
      :rtype: None