class_docstr: Returns positive pairs that have distance greater than a margin and negative
  pairs that have distance less than a margin
code: def set_stats(self, pos_pair, neg_pair):
      if self.collect_stats:
          with torch.no_grad():
              self.pos_pair_dist = (
                  torch.mean(pos_pair).item()
                  if len(pos_pair) > 0
                  else 0
              )
              self.neg_pair_dist = (
                  torch.mean(neg_pair).item()
                  if len(neg_pair) > 0
                  else 0
              )
  
imports: import torch
  from ..utils import loss_and_miner_utils
  from .base_miner import BaseMiner
label_desc: Use image node_id 3 for calling the PairMarginMiner obj's underlying member method code with example usage: obj.set_stats(pos_pair, neg_pair) without return types