def METHOD_NAME(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)