groupBy with a list or an array of closures as it's parameter for nested grouping

def grouped = [
    [aa: 11, bb: 22, cc: 33],
    [aa: 22, bb: 22, cc: 44],
    [aa: 11, bb: 22, cc: 55],
    [aa: 22, bb: 33, cc: 66],
    [aa: 33, bb: 44, cc: 77]
].groupBy({ it.aa }, { it.bb })

def expected = [
    11:[22:[[aa:11, bb:22, cc:33], [aa:11, bb:22, cc:55]]],
    22:[22:[[aa:22, bb:22, cc:44]], 33:[[aa:22, bb:33, cc:66]]],
    33:[44:[[aa:33, bb:44, cc:77]]]
]

assert grouped[11][22] == [[aa:11, bb:22, cc:33], [aa:11, bb:22, cc:55]]
assert grouped[22][33] == [[aa:22, bb:33, cc:66]]
assert grouped[11][99] == null