def append_flipped_images_for_segmentation(self, segdb):
        """
        append flipped images to an roidb
        flip boxes coordinates, images will be actually flipped when loading into network
        :param segdb: [image_index]['seg_cls_path', 'flipped']
        :return: segdb: [image_index]['seg_cls_path', 'flipped']
        """
        print 'append flipped images to segdb'
        assert self.num_images == len(segdb)
        pool = Pool(processes=1)
        pool_result = []
        for i in range(self.num_images):
            seg_rec = segdb[i]
            pool_result.append(pool.apply_async(get_flipped_entry_outclass_wrapper, args=(self, seg_rec, )))
            #self.get_flipped_entry(seg_rec, segdb_flip, i)
        pool.close()
        pool.join()
        segdb_flip = [res_instance.get() for res_instance in pool_result]
        segdb += segdb_flip
        self.image_set_index *= 2
        return segdb

        append flipped images to an roidb
        flip boxes coordinates, images will be actually flipped when loading into network
        :param segdb: [image_index]['seg_cls_path', 'flipped']
        :return: segdb: [image_index]['seg_cls_path', 'flipped']
        
lib/dataset/imdb.py