class_docstr: ArcFace (https://arxiv.org/pdf/1801.07698v1.pdf):
      
code: def forward(self, logits: torch.Tensor, labels: torch.Tensor):
      index = torch.where(labels != -1)[0]
      target_logit = logits[index, labels[index].view(-1)]
  
      with torch.no_grad():
          target_logit.arccos_()
          logits.arccos_()
          final_target_logit = target_logit + self.margin
          logits[index, labels[index].view(-1)] = final_target_logit
          logits.cos_()
      logits = logits * self.s
      return logits
  
file_path: insightface/recognition/arcface_torch/losses.py
imports: import torch
  import math
label_desc: Use image node_id 2 for calling the ArcFace obj's underlying member method code with example usage: obj.forward(logits, labels) and returns: logits