docstr: Returns average metric value for all model outputs.
  Possible format: {metric_name: metric_value}
code: def avg_value(self):
      """
      Returns average metric value for all model outputs.
      Possible format: {metric_name: metric_value}
      """
      return {self._name: self.metric.compute()[self._name].item()}
  
imports: import os
  import time
  import json
  import copy
  import cv2
  import numpy
  import torch
  from torchmetrics.detection.mean_ap import MeanAveragePrecision
  import torchvision
  from pycocotools.coco import COCO
  from pycocotools.cocoeval import COCOeval
  from compression.api import DataLoader, Metric
label_desc: Use image node_id 3 for calling the MAPMetric obj's underlying member method code with example usage: obj.avg_value() and returns: dict