class_docstr: RCNN accuracy. 
docstr: Updates the internal evaluation result. 
docstr_tok: ["Updates","the","internal","evaluation","result","."]
code: def update(self, labels, preds):
      """Updates the internal evaluation result."""
      # label = [rcnn_label]
      # pred = [rcnn_cls]
      rcnn_label = labels[0]
      rcnn_cls = preds[0]
  
      # calculate num_acc
      pred_label = mx.nd.argmax(rcnn_cls, axis=-1)
      num_acc = mx.nd.sum(pred_label == rcnn_label)
  
      self.sum_metric += num_acc.asscalar()
      self.num_inst += rcnn_label.size
  
imports: import mxnet
label_desc: Use image node_id 2 for calling the RCNNAccMetric obj's underlying member method code with example usage: obj.update(labels, preds) without return types