doc: Add hint towards using ArgumentParser.add_argument_group (#5911)

* doc: Add hint towards using ArgumentParser.add_argument_group

Since pl adds many arguments, it is nice to distinguish these arguments

* fixup! address review

Co-authored-by: chaton <thomas@grid.ai>

docs/source/common/trainer.rst

@@ -128,7 +128,10 @@ So you can run it like so:
 
     if __name__ == '__main__':
         parser = ArgumentParser()
-        parser = Trainer.add_argparse_args(parser)
+        parser = Trainer.add_argparse_args(
+            # group the Trainer arguments together
+            parser.add_argument_group(title="pl.Trainer args")
+        )
         args = parser.parse_args()
 
         main(args)

tests/trainer/test_trainer_cli.py

@@ -67,6 +67,21 @@ def test_add_argparse_args_redefined(cli_args):
     assert isinstance(trainer, Trainer)
 
 
+@pytest.mark.parametrize('cli_args', [
+    ['--accumulate_grad_batches=22'],
+    ['--weights_save_path=./'],
+    []
+])
+def test_add_argparse_via_argument_group(cli_args):
+    """Simple test ensuring that passing an argument group still works"""
+    parser = ArgumentParser(add_help=False)
+    parser = Trainer.add_argparse_args(
+        parser.add_argument_group(title="pl.Trainer args")
+    )
+    args = parser.parse_args(cli_args)
+    assert Trainer.from_argparse_args(args)
+
+
 def test_get_init_arguments_and_types():
     """Asserts a correctness of the `get_init_arguments_and_types` Trainer classmethod."""
     args = argparse.get_init_arguments_and_types(Trainer)