code: def update(self, labels, preds):
      loss = preds[0].asnumpy()[0]
      self.sum_metric += loss
      self.num_inst += 1.0
  
file_path: insightface/alignment/heatmap/metric.py
imports: import mxnet
  import numpy
  import math
  import cv2
  from config import config
label_desc: Use image node_id 2 for calling the LossValueMetric obj's underlying member method code with example usage: obj.update(labels, preds) without return types