def __init__(self, *maps):
        self.maps = list(maps) or [{}]          # always at least one map
cross(u, v) --> VectorN
dataset/ETHPy150Open ionelmc/python-aspectlib/src/aspectlib/py2chainmap.py/ChainMap.__init__--crossover with--dataset/ETHPy150Open CountZer0/PipelineConstructionSet/python/maya/site-packages/pymel-1.0.3/pymel/util/arrays.py/cross