def parent(a, b):
    """
    Tests if `a` is a parent of `b` in the Williams & Beer lattice of antichains.

    Parameters
    ----------
    a : iterable of iterables
        One antichain.
    b : iterable of iterables
        Another antichain.

    Returns
    -------
    parent : bool
        True if, for each set in `b`, there exists a set in `a` which is a subset of that set.
    """
    return all(any(frozenset(aa) <= frozenset(bb) for aa in a) for bb in b)