code: def compute_mat(self, query_emb, ref_emb):
      anchor_variances = torch.var(query_emb, dim=1)
      pairwise_diffs = query_emb.unsqueeze(1) - ref_emb
      pairwise_variances = torch.var(pairwise_diffs, dim=2)
      return pairwise_variances / (anchor_variances.unsqueeze(1))
  
imports: import torch
  from .base_distance import BaseDistance
label_desc: Use image node_id 2 for calling the SNRDistance obj's underlying member method code with example usage: obj.compute_mat(query_emb, ref_emb) and returns: unknown