Strategy to use with tfds.testing.mock_data to mock the dataset.

AUTO Try USE_FILES, and fallback to USE_CODE if the metadata files (dataset_info.json,...) are not found.
USE_FILES Load dataset from the metadata files (present in the data_dir kwarg of tfds.testing.mock_data, raise error if data_dir is not reachable.
USE_CODE Load the data from the original dataset generation class. Do not use any generated files. More is more convenient but less safe than USE_FILES. Not all features might be available (e.g. no split-names).

AUTO <MockPolicy.AUTO: 1>
USE_CODE <MockPolicy.USE_CODE: 2>