So siehts ganz gut aus !

node_modules/core-js/modules/es6.object.seal.js

@@ -0,0 +1,9 @@
+// 19.1.2.17 Object.seal(O)
+var isObject = require('./_is-object');
+var meta = require('./_meta').onFreeze;
+
+require('./_object-sap')('seal', function ($seal) {
+  return function seal(it) {
+    return $seal && isObject(it) ? $seal(meta(it)) : it;
+  };
+});