docs: @Override
      public IPortletUrlBuilder getPortletUrlBuilder(IPortletWindowId portletWindowId) {
          IPortletUrlBuilder portletUrlBuilder;
  
          synchronized (this.portletUrlBuilders) {
              portletUrlBuilder = this.portletUrlBuilders.get(portletWindowId);
              if (portletUrlBuilder == null) {
                  portletUrlBuilder = new FailSafePortletUrlBuilder(portletWindowId, this);
                  this.portletUrlBuilders.put(portletWindowId, portletUrlBuilder);
              }
          }
  
          return portletUrlBuilder;
      }