def __iter__(self):
        for key in self._distmap.keys():
            if self[key]:
                yield key
Returns slice of data element if the item is deep
dataset/ETHPy150Open anzev/hedwig/build/pip/pip/_vendor/pkg_resources/__init__.py/Environment.__iter__--crossover with--dataset/ETHPy150Open ioam/holoviews/holoviews/core/ndmapping.py/MultiDimensionalMapping._dataslice