Adding Optional annotation for output-file and replace os.mkdir with …

…Path.mkdir.

mlcube/mlcube/__main__.py

@@ -681,7 +681,7 @@ def inspect(
  platform: str,
  force: bool = False,
  format_: str = "json",
- output_file: str = None,
+ output_file: t.Optional[str] = None,
 ) -> None:
  """Return low-level information on MLCube objects."""
  runner_cls, mlcube_config = parse_cli_args(
@@ -693,7 +693,7 @@ def inspect(
  output_stream = sys.stdout
  else:
  dir_path = Path(output_file).resolve().parent
- os.makedirs(dir_path, exist_ok=True)
+ dir_path.mkdir(parents=True, exist_ok=True)
  output_stream = open(output_file, "w")
 
  try: