public function addParentLocation($parentLocation)
    {
        $locationObject = $this->convertToLocationObject($parentLocation);

        if (!isset($locationObject->data['parent_location_id']) || (int) $locationObject->data['parent_location_id'] < 1) {
            throw new InvalidDataStructureException('Parent location id must be an integer of 2 or above.');
        }

        if (!isset($locationObject->data['content_id'])) {
            if ($this->getProperty('id')) {
                $locationObject->data['content_id'] = $this->getProperty('id');
            }
        }

        $this->properties['parent_locations'][$locationObject->data['parent_location_id']] = $locationObject;
    }