def reduce(self, dimensions=[], function=None, **reduce_map):
        raise NotImplementedError
Yield the subkeys of a registry key as :class:`Registry` objects
dataset/ETHPy150Open ioam/holoviews/holoviews/core/element.py/Element.reduce--crossover with--dataset/ETHPy150Open tjguk/winsys/winsys/registry.py/keys