def METHOD_NAME(self, xblock):
    """ Mock the submission_mixin._get_url_by_file_key method since it relies on the backend. """
    with patch.object(xblock.__class__, '_get_url_by_file_key') as mocked_get:
        mocked_get.side_effect = lambda file_key: f"www.file_url.com/{file_key}"
        yield mocked_get