text: function _classCallCheck(instance, Constructor) {
      if (!(instance instanceof Constructor)) {
          throw new TypeError("Cannot call a class as a function");
      }
  }
  var B = function B() {
      "use strict";
      _classCallCheck(this, B);
      _prop.set(this, {
          writable: true,
          value: void 0
      });
  };
  var _prop = new WeakMap();
  