def test_dont_run_all_dependents_too_early(abcde):
    """From https://github.com/dask/dask-ml/issues/206#issuecomment-395873372."""
    a, b, c, d, e = abcde
    depth = 10
    dsk = {(a, 0): 0, (b, 0): 1, (c, 0): 2, (d, 0): (f, (a, 0), (b, 0), (c, 0))}
    for i in range(1, depth):
        dsk[(b, i)] = (f, (b, 0))
        dsk[(c, i)] = (f, (c, 0))
        dsk[(d, i)] = (f, (d, i - 1), (b, i), (c, i))
    o = order(dsk)
    expected = [3, 6, 9, 12, 15, 18, 21, 24, 27, 30]
    actual = sorted(v for (letter, num), v in o.items() if letter == d)
    assert expected == actual
From https://github.com/dask/dask-ml/issues/206#issuecomment-395873372.
tests/core/serve/test_dag/test_order.py