protected function _getObjects(array $labels = array())
    {
        $objects = array();

        foreach ($labels as $label)
        {
            $method = 'getActivity' . ucfirst($label);

            if (method_exists($this, $method))
            {
                $object = $this->$method();

                if ($object instanceof ComActivitiesActivityObjectInterface) {
                    $objects[$label] = $object;
                }
            }
        }

        return $objects;
    }