class_docstr: Metric with ground truth object location and predicted object label from detector
code: def __init__(self, topk=20, iou_thresh=0.99):
      super(PhrCls, self).__init__("phrcls@%d" % (topk))
      self.topk = topk
      self.iou_thresh = iou_thresh
  
imports: import logging
  import time
  from operator import attrgetter, itemgetter
  import dgl
  import mxnet
  import numpy
  from dgl.nn.mxnet import GraphConv
  from dgl.utils import toindex
  from gluoncv.data.batchify import Pad
  from gluoncv.model_zoo import get_model
  from mxnet import gluon, nd
  from mxnet.gluon import nn
label_desc: Use image node_id 1 to create a new PhrCls object from inherited base classes: mx.metric with example: obj = PhrCls(topk, iou_thresh)