code: def print_coco_metrics(self, json_file):
          
          from pycocotools.cocoeval import COCOeval
          ret = {}
          cocoDt = self.coco.loadRes(json_file)
          cocoEval = COCOeval(self.coco, cocoDt, 'bbox')
          cocoEval.evaluate()
          cocoEval.accumulate()
          cocoEval.summarize()
          fields = ['IoU=0.5:0.95', 'IoU=0.5', 'IoU=0.75', 'small', 'medium', 'large']
          for k in range(6):
              ret['mAP(bbox)/' + fields[k]] = cocoEval.stats[k]
  
          json_obj = json.load(open(json_file))
          if len(json_obj) > 0 and 'segmentation' in json_obj[0]:
              cocoEval = COCOeval(self.coco, cocoDt, 'segm')
              cocoEval.evaluate()
              cocoEval.accumulate()
              cocoEval.summarize()
              for k in range(6):
                  ret['mAP(segm)/' + fields[k]] = cocoEval.stats[k]
          return ret
docs: Args:
              json_file (str): path to the results json file in coco format
          Returns:
              dict: the evaluation metrics