code: public static void initComponentInstanceFields(IsVueComponent vueComponentInstance,
        IsVueComponent javaComponentClassInstance) {
      JsPropertyMap<Object> vueComponentInstancePropertyMap = Js.cast(vueComponentInstance);
      JsPropertyMap<Object> javaComponentClassInstancePropertyMap = Js
          .cast(javaComponentClassInstance);
  
      javaComponentClassInstancePropertyMap.forEach(key -> {
        try {
          if (!javaComponentClassInstancePropertyMap.has(key)
              || vueComponentInstancePropertyMap.get(key) != null) {
            return;
          }
          vueComponentInstancePropertyMap.set(key, javaComponentClassInstancePropertyMap.get(key));
        } catch (Exception e) {
  
        }
      });
    }
docs: Init instance properties for the given VueComponent instance. The Constructor for VueComponent
  is provided by Vue and doesn't extend the {@link IsVueComponent} constructor. This method get
  an instance of the Java class for the VueComponent and copy properties to the
  VueComponentInstance. This will initialise properties that are initialised inline in the class.
  For example: List&lt;String&gt; myList = new LinkedList&lt;String&gt;();
  
  @param vueComponentInstance An instance of VueComponent to initialize
  @param javaComponentClassInstance An instance of the Component class