AVAMeter explain

Hi, I'm new on slowfast.

I trained with my custom data, but I don't really understand stats in log.

```
[11/18 19:39:49][INFO] logging.py: 99: json_stats: {"_type": "train_iter", "dt": 4.99287, "dt_data": 0.00628, "dt_net": 4.98658, "epoch": "10/50", "eta": "8:54:59", "gpu_mem": "4.68G", "iter": "90/159", "loss": 2.40392, "lr": 0.00038, "top1_err": 12.50000, "top5_err": 0.00000}
[11/18 19:40:36][INFO] logging.py: 99: json_stats: {"_type": "train_iter", "dt": 4.82072, "dt_data": 0.00632, "dt_net": 4.81440, "epoch": "10/50", "eta": "8:35:44", "gpu_mem": "4.68G", "iter": "100/159", "loss": 2.48380, "lr": 0.00038, "top1_err": 12.50000, "top5_err": 0.00000}

```

I found it in code, but I don't see comment about it


I searched on google, but there is a few results about it.

Specifically, iter_timer, data_iter, net_timer, what are those?

Please, explained for me. Thank you so much