from typing import Any
from typing import Tuple


def _normalize_slice_key(key: Any) -> Tuple:
    """ Normalizes slice key into always being a top-level tuple.

    Args:
        key: Slicing key that is passed within __getitem__.

    Returns:
        Expanded slice as a tuple.
    """
    if not isinstance(key, tuple):
        return (key,)
    else:
        return key