code: protected function getValidXmlElementName($name)
      {
          if (empty($name) || is_int($name) || !$this->isValidXmlName($name)) {
              return $this->itemTag;
          }
  
          return $name;
      }
docs: Returns element name ready to be used in DOMElement if
  name is not empty, is not int and is valid.
  
  Falls back to [[itemTag]] otherwise.
  
  @param mixed $name
  @return string
  @since 2.0.12