Add model saving for qrun and workflow example

examples/workflow_by_code.py

@@ -112,6 +112,7 @@ if __name__ == "__main__":
     with R.start(experiment_name="workflow"):
         R.log_params(**flatten_dict(task))
         model.fit(dataset)
+        R.save_objects(**{"params.pkl": model})
 
         # prediction
         recorder = R.get_recorder()

qlib/model/trainer.py

@@ -26,6 +26,7 @@ def task_train(task_config: dict, experiment_name):
         R.log_params(**flatten_dict(task_config))
         model.fit(dataset)
         recorder = R.get_recorder()
+        R.save_objects(**{"params.pkl": model})
 
         # generate records: prediction, backtest, and analysis
         for record in task_config["record"]: