def gt_roidb(self):
        """
        return ground truth image regions database
        :return: imdb[image_index]['boxes', 'gt_classes', 'gt_overlaps', 'flipped']
        """
        cache_file = os.path.join(self.cache_path, self.name + '_gt_roidb.pkl')
        if os.path.exists(cache_file):
            with open(cache_file, 'rb') as fid:
                roidb = cPickle.load(fid)
            print '{} gt roidb loaded from {}'.format(self.name, cache_file)
            return roidb

        gt_roidb = [self.load_pascal_annotation(index) for index in self.image_set_index]
        with open(cache_file, 'wb') as fid:
            cPickle.dump(gt_roidb, fid, cPickle.HIGHEST_PROTOCOL)
        print 'wrote gt roidb to {}'.format(cache_file)

        return gt_roidb

        return ground truth image regions database
        :return: imdb[image_index]['boxes', 'gt_classes', 'gt_overlaps', 'flipped']
        
lib/dataset/pascal_voc.py