code: public function setHeadTitle(string $title) : self
      {
          if (!$this->headTitle) {
              $this->headTitle = new HtmlElement('<title>');
              $this->head->addFirst($this->headTitle);
          }
          $this->headTitle->setContent($title);
  
          return $this;
      }
docs: @param string $title
  
  @return $this|self