docs: public void doFilter(RenderRequest request, RenderResponse response, FilterChain chain) throws IOException,
              PortletException {
  
          // Lazily initialize the delegate if necessary.
          initDelegate(true);
  
          if (this.renderDelegate == null) {
              throw new IllegalStateException("The delegate PortletFilter does not implement RenderFilter but " + this.getFilterName() + " is configured with the RENDER_PHASE lifecycle.");
          }
  
          // Let the delegate perform the actual doFilter operation.
          invokeDelegate(this.renderDelegate, request, response, chain);
      }