We can filter stock by dollar volume in coarse:

    def MyCoarseFilterFunction(self, coarse):
         sortedByDollarVolume = sorted(coarse, key=lambda x: x.DollarVolume, reverse=True)
         return filtered[:100]

This looks at daily volume. but what if we want to look at monthly volume? That is, we want 100 most liquid stocks by monthly volume?