How to use the gluoncv.utils.metrics.coco_detection.COCODetectionMetric function in gluoncv

def __init__(self, dataset, save_prefix, use_time=True, cleanup=False, score_thresh=0.05,
                 data_shape=None, post_affine=None):
        super(COCODetectionMetric, self).__init__('COCOMeanAP')
        self.dataset = dataset
        self._img_ids = sorted(dataset.coco.getImgIds())
        self._current_id = 0
        self._cleanup = cleanup
        self._results = []
        self._score_thresh = score_thresh
        if isinstance(data_shape, (tuple, list)):
            assert len(data_shape) == 2, "Data shape must be (height, width)"
        elif not data_shape:
            data_shape = None
        else:
            raise ValueError("data_shape must be None or tuple of int as (height, width)")
        self._data_shape = data_shape
        if post_affine is not None:
            assert self._data_shape is not None, "Using post affine transform requires data_shape"
            self._post_affine = post_affine

def get_dataset(dataset, args):
    if dataset.lower() == 'voc':
        val_dataset = gdata.VOCDetection(
            splits=[(2007, 'test')])
        val_metric = VOC07MApMetric(iou_thresh=0.75, class_names=val_dataset.classes)
    elif dataset.lower() == 'coco':
        val_dataset = gdata.COCODetection(splits='instances_val2017', skip_empty=False)
        val_metric = COCODetectionMetric(val_dataset, args.save_prefix + '_eval',
                                         cleanup=not args.save_json)
    else:
        raise NotImplementedError('Dataset: {} not implemented.'.format(dataset))
    return val_dataset, val_metric

def get_dataset(dataset, args):
    if dataset.lower() == 'voc':
        val_dataset = gdata.VOCDetection(
            splits=[(2007, 'test')])
        val_metric = VOC07MApMetric(iou_thresh=0.75, class_names=val_dataset.classes)
    elif dataset.lower() == 'coco':
        val_dataset = gdata.COCODetection(splits='instances_val2017', skip_empty=False)
        val_metric = COCODetectionMetric(val_dataset, args.save_prefix + '_eval',
                                         cleanup=not args.save_json)
    else:
        raise NotImplementedError('Dataset: {} not implemented.'.format(dataset))
    return val_dataset, val_metric

def get_dataset(dataset, data_shape):
    if dataset.lower() == 'voc':
        val_dataset = gdata.VOCDetection(splits=[(2007, 'test')])
        val_metric = VOC07MApMetric(iou_thresh=0.5, class_names=val_dataset.classes)
    elif dataset.lower() == 'coco':
        val_dataset = gdata.COCODetection(splits='instances_val2017', skip_empty=False)
        val_metric = COCODetectionMetric(
            val_dataset, args.save_prefix + '_eval', cleanup=True,
            data_shape=(data_shape, data_shape), post_affine=get_post_transform)
    else:
        raise NotImplementedError('Dataset: {} not implemented.'.format(dataset))
    return val_dataset, val_metric

def get_dataset(dataset, args):
    if dataset.lower() == 'voc':
        train_dataset = gdata.VOCDetection(
            splits=[(2007, 'trainval'), (2012, 'trainval')])
        val_dataset = gdata.VOCDetection(
            splits=[(2007, 'test')])
        val_metric = VOC07MApMetric(iou_thresh=0.5, class_names=val_dataset.classes)
    elif dataset.lower() == 'coco':
        train_dataset = gdata.COCODetection(root=args.dataset_root + "/coco", splits='instances_train2017')
        val_dataset = gdata.COCODetection(root=args.dataset_root + "/coco", splits='instances_val2017', skip_empty=False)
        val_metric = COCODetectionMetric(
            val_dataset, args.save_prefix + '_eval', cleanup=True,
            data_shape=(args.data_shape, args.data_shape), post_affine=get_post_transform)
        # coco validation is slow, consider increase the validation interval
        if args.val_interval == 1:
            args.val_interval = 10
    else:
        raise NotImplementedError('Dataset: {} not implemented.'.format(dataset))
    if args.num_samples < 0:
        args.num_samples = len(train_dataset)
    return train_dataset, val_dataset, val_metric

def get_dataset(dataset, args):
    if dataset.lower() == 'voc':
        train_dataset = gdata.VOCDetection(
            splits=[(2007, 'trainval'), (2012, 'trainval')])
        val_dataset = gdata.VOCDetection(
            splits=[(2007, 'test')])
        val_metric = VOC07MApMetric(iou_thresh=0.5, class_names=val_dataset.classes)
    elif dataset.lower() == 'coco':
        train_dataset = gdata.COCODetection(splits='instances_train2017')
        val_dataset = gdata.COCODetection(splits='instances_val2017', skip_empty=False)
        val_metric = COCODetectionMetric(val_dataset, args.save_prefix + '_eval', cleanup=True)
    else:
        raise NotImplementedError('Dataset: {} not implemented.'.format(dataset))
    return train_dataset, val_dataset, val_metric

def get_dataset(dataset, args):
    if dataset.lower() == 'voc':
        train_dataset = gdata.VOCDetection(
            splits=[(2007, 'trainval'), (2012, 'trainval')])
        val_dataset = gdata.VOCDetection(
            splits=[(2007, 'test')])
        val_metric = VOC07MApMetric(iou_thresh=0.5, class_names=val_dataset.classes)
    elif dataset.lower() == 'coco':
        train_dataset = gdata.COCODetection(root=args.dataset_root + "/coco", splits='instances_train2017')
        val_dataset = gdata.COCODetection(root=args.dataset_root + "/coco", splits='instances_val2017', skip_empty=False)
        val_metric = COCODetectionMetric(
            val_dataset, args.save_prefix + '_eval', cleanup=True,
            data_shape=(args.data_shape, args.data_shape))
        # coco validation is slow, consider increase the validation interval
        if args.val_interval == 1:
            args.val_interval = 10
    else:
        raise NotImplementedError('Dataset: {} not implemented.'.format(dataset))
    return train_dataset, val_dataset, val_metric

def get_dataset(dataset, args):
    if dataset.lower() == 'voc':
        train_dataset = gdata.VOCDetection(
            splits=[(2007, 'trainval'), (2012, 'trainval')])
        val_dataset = gdata.VOCDetection(
            splits=[(2007, 'test')])
        val_metric = VOC07MApMetric(iou_thresh=0.5, class_names=val_dataset.classes)
    elif dataset.lower() == 'coco':
        train_dataset = gdata.COCODetection(splits='instances_train2017', use_crowd=False)
        val_dataset = gdata.COCODetection(splits='instances_val2017', skip_empty=False)
        val_metric = COCODetectionMetric(val_dataset, args.save_prefix + '_eval', cleanup=True)
    else:
        raise NotImplementedError('Dataset: {} not implemented.'.format(dataset))
    if args.mixup:
        from gluoncv.data.mixup import detection
        train_dataset = detection.MixupDetection(train_dataset)
    return train_dataset, val_dataset, val_metric

def metrics(self):
        _, _, H, W = self.ishape
        metric = COCODetectionMetric(
            self.val_dataset, '_eval', cleanup=True, data_shape=(H, W))
        metric.reset()
        return metric