code: private function _cacheCustomFields($class)
      {
          $customFieldsGroups = $this->em->getRepository('ChillCustomFieldsBundle:CustomFieldsGroup')
              ->findBy(array('entity' => (is_string($class)) ? $class : get_class($class)));
          
          if (!$customFieldsGroups) {
              throw CustomFieldsHelperException::customFieldsGroupNotFound((is_string($class)) ? $class : get_class($class));
          }
          
          foreach ($customFieldsGroup as $cfGroup) {
              $this->_cacheCustomFields($cfGroup);
          }
      }
docs: Set in cache all the custom fields of a given class containing some
  custom fields.
  
  @param object|string $class The given class.
  @todo check if this fucntions has to call _cacheCustomFieldsGroup instead of
  _cacheCustomFields ?