def relerr(expected, actual):
    return abs((actual - expected)/expected)
return a flattened list of members.  equivalent to `ObjectSet.members(flatten=True)`
dataset/ETHPy150Open probcomp/bayeslite/src/math_util.py/relerr--crossover with--dataset/ETHPy150Open CountZer0/PipelineConstructionSet/python/maya/site-packages/pymel-1.0.3/pymel/core/nodetypes.py/ObjectSet.flattened