protected function _parseConditionGroup($condition = null) {
		$result = 'AND';
		if (empty($condition)) {
			return $result;
		}

		$condition = (string)mb_convert_case($condition, MB_CASE_UPPER);
		if (in_array($condition, ['AND', 'OR', 'NOT'])) {
			$result = $condition;
		}

		return $result;
	}