code: public function addTemplateSlots($templateName, $username)
      {
          if (!array_key_exists($templateName, $this->templateBlocks)) {
              return null;
          }
  
          $blocks = $this->templateBlocks[$templateName];
          $this->addSlots($blocks, $username);
      }
docs: Adds the default theme slots to the page which uses the given template
  
  @param string $templateName
  @param string $username