fix(pt): ensure suffix of --init_model and --restart is .pt (de…

…epmodeling#3980)

... as in the command line help, we say "path prefix of checkpoint
files". This will be compatible with the current DP-GEN code.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Bug Fixes**
- Ensured that the `.pt` suffix is automatically appended to
`init_model` and `restart` file paths if not already present.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Signed-off-by: Jinzhe Zeng <[email protected]>

deepmd/pt/entrypoints/main.py

@@ -236,6 +236,11 @@ def train(FLAGS):
     SummaryPrinter()()
     with open(FLAGS.INPUT) as fin:
         config = json.load(fin)
+    # ensure suffix, as in the command line help, we say "path prefix of checkpoint files"
+    if FLAGS.init_model is not None and not FLAGS.init_model.endswith(".pt"):
+        FLAGS.init_model += ".pt"
+    if FLAGS.restart is not None and not FLAGS.restart.endswith(".pt"):
+        FLAGS.restart += ".pt"
 
     # update multitask config
     multi_task = "model_dict" in config["model"]