code: public function _getElementHtml(AbstractElement $element)
      {
          $this->setNamePrefix($element->getName())
              ->setHtmlId($element->getHtmlId());
  
          return $this->_toHtml();
      }
docs: Retrieve element HTML markup.
  
  @param \Magento\Framework\Data\Form\Element\AbstractElement $element
  @return string