def get_by_object(self, val):
        oset = self.objmap.get(id(val), None)
        if oset:
            return list(oset)[0]
        return None
Check whether a value is in the cache. This is keyed by the
dataset/ETHPy150Open erkyrath/tworld/lib/two/propcache.py/PropCache.get_by_object