     /// - Parameters:
     ///   - trackingId: your Universal Analytics ID
     func initialize(_ parameters: [AnyHashable: Any]) {
-        if let trackingId = parameters["trackingId"] {
+        if let trackingId = parameters[TRACKING_ID] {
             self.tracker = self.instance.tracker(withTrackingId: trackingId as! String);
             // the SDK is now initialized
             self.initialized = true;
-            logger.logParamSetWithSuccess("trackingId", value: trackingId);
-        }
-        else {
-            logger.logMissingParam("trackingId", methodName: "GA_init");
+            logger.logParamSetWithSuccess(TRACKING_ID, value: trackingId);
+        }
+        else {
+            logger.logMissingParam(TRACKING_ID, methodName: GA_INIT);
         }
     }
 

            let builder: NSObject = GAIDictionaryBuilder.createScreenView().build();
            // send the screen event
            self.tracker.send(builder as! [NSObject : AnyObject]);
        }
        else {
            logger.logMissingParam(SCREEN_NAME, methodName: "GA_tagScreen");
        }
    }
    

        self.instance = GAI.sharedInstance();
        self.tracker = self.instance.defaultTracker;

        cargo.registerTagHandler(self, key: GA_INIT);
        cargo.registerTagHandler(self, key: GA_SET);
        cargo.registerTagHandler(self, key: GA_IDENTIFY);
        cargo.registerTagHandler(self, key: GA_TAG_SREEN);
        cargo.registerTagHandler(self, key: GA_TAG_EVENT);
    }

    /// Callback from GTM container designed to execute a specific method
