keras/src/trainers/data_adapters/py_dataset_adapter.py/get_index
def get_index(uid, i):
    """Get the value from the PyDataset `uid` at index `i`.

    To allow multiple PyDatasets to be used at the same time, we use `uid` to
    get a specific one. A single PyDataset would cause the validation to
    overwrite the training PyDataset.

    Args:
        uid: int, PyDataset identifier
        i: index

    Returns:
        The value at index `i`.
    """
    return _SHARED_SEQUENCES[uid][i]