def test_intersection_ab(a, b):
    intAB = (a & b)
    assert (not intAB.accepts(''))
    assert (not intAB.accepts('a'))
    assert (not intAB.accepts('b'))
def test_intersection_ab(a, b):
    intAB = (a & b)
    assert (not intAB.accepts())
    assert (not intAB.accepts('a'))
    assert (not intAB.accepts('b'))