code: public function refreshSections()
      {
          if ($this->id === null) {
              return [];
          }
  
          $this->fields['IBLOCK_SECTION'] = [];
          $dbSections = static::$bxObject->getElementGroups($this->id, true);
          while ($section = $dbSections->Fetch()) {
              $this->fields['IBLOCK_SECTION'][] = $section;
          }
  
          $this->sectionsAreFetched = true;
  
          return $this->fields['IBLOCK_SECTION'];
      }
docs: Refresh element's sections and save them to a class field.
  
  @return array