Document::getRealCategoryId

public function getRealCategoryId()
{
	$runtime = CBPRuntime::GetRuntime();
	$runtime->StartRuntime();
	$documentService = $runtime->GetService('DocumentService');

	$this->fillSession();
	$session = $this->getSession();

	return $documentService->getFieldValue(
		$this->getParameterDocumentId(),
		'CATEGORY_ID',
		$session->getParameterDocumentType()
	);
}