code: function get(key) {
          var state = getInternalState(this);
          if (isObject(key)) {
            var data = getWeakData(key);
            if (data === true) return uncaughtFrozenStore(state).get(key);
            return data ? data[state.id] : undefined;
          }
        }
docs: 23.3.3.3 WeakMap.prototype.get(key)