What are the pairwise parameters mean?

[jingshaoli]

There are 4 pairwise parameters in coco/train/pose_cfg.yaml,they are
pairwise_predict: true
pairwise_huber_loss: true
pairwise_loss_weight: 0.05
pairwise_stats_fn: ../pairwise/pairwise_stats.mat

Could you tell me what are they mean,especially the pairwise_stats.mat