docs: private static UIComponent createFacetUIPanel(FaceletContext ctx, UIComponent parent, String facetName)
      {
          FacesContext facesContext = ctx.getFacesContext();
          UIComponent panel = facesContext.getApplication().createComponent(facesContext, UIPanel.COMPONENT_TYPE, null);
          
          // The panel created by this method is special. To be restored properly and do not
          // create duplicate ids or any other unwanted conflicts, it requires an unique id.
          // This code is usually called when more than one component is added to a facet and
          // it is necessary to create a shared container.
          // Use FaceletCompositionContext.generateUniqueComponentId() is not possible, because
          // <c:if> blocks inside a facet will make component ids unstable. Use UniqueIdVendor
          // is feasible but also will be affected by <c:if> blocks inside a facet.
          // The only solution that will generate real unique ids is use the parent id and the
          // facet name and derive an unique id that cannot be generated by SectionUniqueIdCounter,
          // doing the same trick as with metadata: use a double __ and add a prefix (f).
          // Note this id will never be printed into the response, because this is just a container.
          FaceletCompositionContext mctx = FaceletCompositionContext.getCurrentInstance(ctx);
          UniqueIdVendor uniqueIdVendor = mctx.getUniqueIdVendorFromStack();
          if (uniqueIdVendor == null)
          {
              uniqueIdVendor = ComponentSupport.getViewRoot(ctx, parent);
          }
          if (uniqueIdVendor != null)
          {
              // UIViewRoot implements UniqueIdVendor, so there is no need to cast to UIViewRoot
              // and call createUniqueId(). See ComponentTagHandlerDelegate
              int index = facetName.indexOf('.');
              String cleanFacetName = facetName;
              if (index >= 0)
              {
                  cleanFacetName = facetName.replace('.', '_');
              }
              panel.setId(uniqueIdVendor.createUniqueId(facesContext, 
                      mctx.getSharedStringBuilder()
                        .append(parent.getId())
                        .append("__f_")
                        .append(cleanFacetName).toString()));
          }
          panel.getAttributes().put(FACET_CREATED_UIPANEL_MARKER, Boolean.TRUE);
          panel.getAttributes().put(ComponentSupport.COMPONENT_ADDED_BY_HANDLER_MARKER, Boolean.TRUE);
          return panel;
      }