make the basic command line clean

bin/jflow_cli.py

@@ -129,7 +129,11 @@ if __name__ == '__main__':
                     pgroup.add_argument(param.flag, **param.export_to_argparse())
         sub_parser.set_defaults(cmd_object=instance.__class__.__name__)
     args = vars(parser.parse_args())
-
+    
+    if not "cmd_object" in args:
+        print(parser.format_help())
+        parser.exit(0, "")
+    
     if args["cmd_object"] in wf_classes:
         wfmanager.run_workflow(args["cmd_object"], args)
     elif args["cmd_object"] == "rerun":