code: public function toNode(DOMDocument $document = null)
      {
          if (null === $document) {
              $document = new DOMDocument();
          }
  
          $node = $document->createElement('EEIFilingOption');
  
          $code = $this->getCode();
          if (isset($code)) {
              $node->appendChild($document->createElement('Code', $code));
          }
  
          $emailAddress = $this->getEmailAddress();
          if (isset($emailAddress)) {
              $node->appendChild($document->createElement('EMailAdress', $emailAddress));
          }
  
          $description = $this->getDescription();
          if (isset($description)) {
              $node->appendChild($document->createElement('Description', $description));
          }
  
          $upsFiled = $this->getUPSFiled();
          if (isset($upsFiled)) {
              $node->appendChild($upsFiled->toNode($document));
          }
  
          $shipperFiled = $this->getShipperFiled();
          if (isset($shipperFiled)) {
              $node->appendChild($shipperFiled->toNode($document));
          }
  
          return $node;
      }
docs: @param null|DOMDocument $document
  
  @return DOMElement