code: protected function renderHelpBlock(ElementInterface $oElement)
      {
          if ($sHelpBlock = $oElement->getOption('help-block')) {
              if ($oTranslator = $this->getTranslator()) {
                  $sHelpBlock = $oTranslator->translate($sHelpBlock, $this->getTranslatorTextDomain());
              }
              $sHelpBlockString = strip_tags($sHelpBlock);
              if ($sHelpBlock === $sHelpBlockString) {
                  $sHelpBlock = $this->getEscapeHtmlHelper()->__invoke($sHelpBlock);
              }
              return sprintf(static::$helpBlockFormat, $sHelpBlock);
          } else {
              return '';
          }
      }
docs: Render element's help block
  @param ElementInterface $oElement
  @return string