def intersect_all(set1: set, set2: set, set3: set) -> set:
    """Return the intersection of all three of the given sets: set1, set2, and set3.

    >>> intersect_all({1, 2, 3}, {1, 2, 3, "test"}, {1, 2, 6, 7, "test"}) == {1, 2}
    True
    >>> intersect_all(set(), {1, 2, 3}, {1, 2, 3}) == set()
    True
    >>> intersect_all({"a", ""}, {1, 0}, {True, False}) == set()
    True
    >>> intersect_all({'a'}, {"a"}, {chr(97)}) == {'a'}
    True
    """
    return set.intersection(set1, set2, set3)