!7215 modify checkpoint warning info

Merge pull request !7215 from changzherui/mod_ckpt_info

mindspore/train/serialization.py

@@ -51,7 +51,8 @@ def _set_pb_env():
     """Set env variable `PROTOCOL_BUFFERS` to prevent memory overflow."""
     if os.getenv("PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION") == "cpp":
         logger.warning("Current env variable `PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp`,\
-            When the parameter is too large, it may cause memory limit error.")
+            When the parameter is too large, it may cause memory limit error.\
+            This can be solved by set env `PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python`.")
     else:
         os.environ["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = "python"
         logger.debug("Set the `PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python`.")