-// create cache frames
- VFrame *new_cache_frame(VFrame *vframe, int64_t position);
- void put_cache_frame();
- int get_use_cache();
+// thie function will be used to verify if all files in a given
+// list are of same size or not. Each list type object should
+// override this method with its own definition.
+ virtual int verify_file_list() { return 1; }