how to replace navigation portlet with my own template file in plone4.3

[nirmala]

can anyone tell how to replace a navigation portlet with my own template. I did like this

1. I created one new class for portlet in my .py file and its look like below

  class navigation_address(Renderer):         
              index = ViewPageTemplateFile('templates/portlet_address.pt')

2. I registered the portlets in overrides.zcml like

      
        <plone:portletRenderer
          portlet="plone.app.portlets.portlets.navigation.INavigationPortlet"
          class=".browser.createPictMenu.navigation_address"
          />