So siehts ganz gut aus !

node_modules/babel-runtime/helpers/classCallCheck.js

@@ -0,0 +1,9 @@
+"use strict";
+
+exports.__esModule = true;
+
+exports.default = function (instance, Constructor) {
+  if (!(instance instanceof Constructor)) {
+    throw new TypeError("Cannot call a class as a function");
+  }
+};