code: def prepare(self, predictions, iou_type):
      if iou_type == "bbox":
          return self.prepare_for_coco_detection(predictions)
      elif iou_type == "segm":
          return self.prepare_for_coco_segmentation(predictions)
      elif iou_type == "keypoints":
          return self.prepare_for_coco_keypoint(predictions)
      else:
          raise ValueError("Unknown iou type {}".format(iou_type))
  
imports: import os
  import contextlib
  import copy
  import numpy
  import torch
  from pycocotools.cocoeval import COCOeval
  from pycocotools.coco import COCO
  import pycocotools.mask
  from util.misc import all_gather
label_desc: Use image node_id 6 for calling the CocoEvaluator obj's underlying member method code with example usage: obj.prepare(predictions, iou_type) and returns: self, self, self