def METHOD_NAME(dataset: Dataset, tag: str) -> Optional[Dataset]:
    """Return a version of dataset that has a specific tag.
    Args:
        dataset(Dataset): A dataset to return its tagged version.
        tag(str): Tag name to search for.
    Returns:
        Optional[Dataset]: The dataset pointed to by the tag or None if nothing found.
    """
    dataset_gateway = DatasetGateway()
    tags = dataset_gateway.get_all_tags(dataset)
    selected_tag = next((t for t in tags if t.name == tag), None)
    if selected_tag is None:
        return None
    return dataset_gateway.get_by_id(selected_tag.dataset_id.value)