Try to do a value lookup from the existing cache entries.

def _get_hit(self, key):
        """Try to do a value lookup from the existing cache entries."""
        try:
            result = self.cache[key]
            self.hits += 1
            self._ref_key(key)
            return result
        except KeyError:
            pass

        result = self.weakrefs[key]
        self.refhits += 1
        self.cache[key] = result
        self._ref_key(key)
        return result