code: def test_s3_shortcut_string(prefix: Optional[str]) -> None:
      bucket = "mybucket"
      shortcut = f"s3://{bucket}"
      if prefix:
          shortcut += f"/{prefix}"
      with mock.patch(
          "determined.common.storage.S3StorageManager"
      ) as mocked:
          _ = storage.from_string(shortcut)
      mocked.assert_called_once_with(bucket=bucket, prefix=prefix)
  
imports: import os
  from typing import Optional
  from unittest import mock
  import pytest
  from determined import core
  from determined.common import storage
label_desc: Use image node_id 9 for calling a global function with example usage: test_s3_shortcut_string(prefix) without return types