code: def metric(self, whs, centers):
      wh1 = whs[:, None]
      wh2 = centers[None]
      inter = np.minimum(wh1, wh2).prod(2)
      return inter / (wh1.prod(2) + wh2.prod(2) - inter)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import sys
  from ppdet.utils.logger import setup_logger
  from scipy.cluster.vq import kmeans
  import numpy
  from tqdm import tqdm
  from ppdet.utils.cli import ArgsParser
  from ppdet.utils.check import check_gpu, check_version, check_config
  from ppdet.core.workspace import load_config, merge_config
label_desc: Use image node_id 3 for calling the YOLOv2AnchorCluster obj's underlying member method code with example usage: obj.metric(whs, centers) and returns: unknown