def sum(a, start=0, axis=None):
    if isinstance(a, Array) :
        axis = a._getaxis(axis, fill=True)
        return reduce(operator.add, a.axisiter(*axis), start)
    elif hasattr(a, '__iter__') :
        return _sum(a, start)
    else :
        return a+start
sum(a[, start=0[, axis=(axis0, axis1, ...)]]) --> numeric or Array
dataset/ETHPy150Open CountZer0/PipelineConstructionSet/python/maya/site-packages/pymel-1.0.3/pymel/util/arrays.py/sum