def postorder( iterable, testFn=isIterable, limit=sys.getrecursionlimit()):
    if limit :
        last = None
        for arg in iterable :
            if testFn(arg) :
                for a in postorderIterArgs (limit-1, testFn, *arg) :
                    yield a
            else :
                if last :
                    yield last
                last = arg
        if last :
            yield last
    else :
        for arg in iterable :
            yield arg
iterator doing a postorder expansion of args
dataset/ETHPy150Open CountZer0/PipelineConstructionSet/python/maya/site-packages/pymel-1.0.3/pymel/util/arguments.py/postorder