protected function _scope($entity) {
		$scope = [];
		foreach ($this->_config['scope'] as $key => $value) {
			if (is_numeric($key)) {
				if (isset($entity, $value)) {
					$scope[$value] = $entity->$value;
				} else {
					$message = "The `{$value}` scope in not present in the entity.";
					throw new UnexpectedValueException($message);
				}
			} else {
				$scope[$key] = $value;
			}
		}
		return $scope;
	}