code: public function getTemplateClass($name, $index = null)
      {
          $key = $this->getLoader()->getCacheKey($name).$this->optionsHash;
  
          return $this->templateClassPrefix.hash('sha256', $key).(null === $index ? '' : '_'.$index);
      }
docs: Gets the template class associated with the given string.
  
  The generated template class is based on the following parameters:
  
  * The cache key for the given template;
  * The currently enabled extensions;
  * Whether the Twig C extension is available or not;
  * PHP version;
  * Twig version;
  * Options with what environment was created.
  
  @param string   $name  The name for which to calculate the template class name
  @param int|null $index The index if it is an embedded template
  
  @return string The template class name