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