So siehts ganz gut aus !

node_modules/core-js/modules/es7.reflect.metadata.js

@@ -0,0 +1,15 @@
+var $metadata = require('./_metadata');
+var anObject = require('./_an-object');
+var aFunction = require('./_a-function');
+var toMetaKey = $metadata.key;
+var ordinaryDefineOwnMetadata = $metadata.set;
+
+$metadata.exp({ metadata: function metadata(metadataKey, metadataValue) {
+  return function decorator(target, targetKey) {
+    ordinaryDefineOwnMetadata(
+      metadataKey, metadataValue,
+      (targetKey !== undefined ? anObject : aFunction)(target),
+      toMetaKey(targetKey)
+    );
+  };
+} });