docs: public void setHandler (@Nonnull final EJSEvent eJSEvent, @Nonnull final IHasJSCode aNewHandler)
    {
      ValueEnforcer.notNull (eJSEvent, "JSEvent");
      ValueEnforcer.notNull (aNewHandler, "NewHandler");
  
      // Set only the new handler and remove any existing handler
      m_aEvents.put (eJSEvent, new CollectingJSCodeProvider ().appendFlattened (aNewHandler));
    }