code: public function getVisiblePanels()
      {
          if ($this->visiblePanels === null) {
              $this->visiblePanels = array();
  
              $panels = $this->getSortedChildBlocks();
              foreach ($panels as $panel) {
                  if (!$panel instanceof Sheep_Debug_Block_Panel) {
                      continue;
                  }
  
                  $this->visiblePanels[] = $panel;
              }
          }
          return $this->visiblePanels;
      }
docs: Returns sorted visible debug panels
  
  @return Sheep_Debug_Block_Panel[]