Then you instantiate this class as: python debug_overflow = DebugUnderflowOverflow(model, trace_batch_nums=[1, 3]) And now full batches 1 and 3 will be traced using the same format as the underflow/overflow detector does. Batches are 0-indexed. This is helpful if you know that the program starts misbehaving after a certain batch number, so you can fast-forward right to that area.