def _get_backend_from_parts(parts: tuple[str, ...]) -> str | None:
    """Return the backend part of a test file's path parts.

    Examples
    --------
    >>> _get_backend_from_parts(("/", "ibis", "backends", "sqlite", "tests"))
    "sqlite"
    """
    try:
        index = parts.index("backends")
    except ValueError:
        return None
    else:
        return parts[index + 1]