code: public function render(FormInterface $oForm, $sFormLayout = self::LAYOUT_HORIZONTAL)
      {
          //Prepare form if needed
          if (method_exists($oForm, 'prepare')) {
              $oForm->prepare();
          }
  
          $this->setFormClass($oForm, $sFormLayout);
  
          //Set form role
          if (!$oForm->getAttribute('role')) {
              $oForm->setAttribute('role', 'form');
          }
  
          return $this->openTag($oForm) . "\n" . $this->renderElements($oForm, $sFormLayout) . $this->closeTag();
      }
docs: Render a form from the provided $oForm,
  @see Form::render()
  @param FormInterface $oForm
  @param string $sFormLayout
  @return string