code: private function getAccountHolder(array $element)
      {
          $firstName = !empty($element['billing']['firstName']) ? $element['billing']['firstName'] : '';
          $lastName = !empty($element['billing']['lastName']) ? $element['billing']['lastName'] : '';
  
          return trim(sprintf('%s %s', $firstName, $lastName));
      }
docs: @param array $element
  
  @return string