def METHOD_NAME(input_filename, output_filename):
    """
    Filter LVIS instance segmentation annotations to remove all categories that are not included in
    COCO. The new json files can be used to evaluate COCO AP using `lvis-api`. The category ids in
    the output json are the incontiguous COCO dataset ids.
    Args:
        input_filename (str): path to the LVIS json file.
        output_filename (str): path to the COCOfied json file.
    """
    with open(input_filename, "r") as f:
        lvis_json = json.load(f)
    lvis_annos = lvis_json.pop("annotations")
    cocofied_lvis = copy.deepcopy(lvis_json)
    lvis_json["annotations"] = lvis_annos
    # Mapping from lvis cat id to coco cat id via synset
    lvis_cat_id_to_synset = {cat["id"]: cat["synset"] for cat in lvis_json["categories"]}
    synset_to_coco_cat_id = {x["synset"]: x["coco_cat_id"] for x in COCO_SYNSET_CATEGORIES}
    # Synsets that we will keep in the dataset
    synsets_to_keep = set(synset_to_coco_cat_id.keys())
    coco_cat_id_with_instances = defaultdict(int)
    new_annos = []
    ann_id = 1
    for ann in lvis_annos:
        lvis_cat_id = ann["category_id"]
        synset = lvis_cat_id_to_synset[lvis_cat_id]
        if synset not in synsets_to_keep:
            continue
        coco_cat_id = synset_to_coco_cat_id[synset]
        new_ann = copy.deepcopy(ann)
        new_ann["category_id"] = coco_cat_id
        new_ann["id"] = ann_id
        ann_id += 1
        new_annos.append(new_ann)
        coco_cat_id_with_instances[coco_cat_id] += 1
    cocofied_lvis["annotations"] = new_annos
    for image in cocofied_lvis["images"]:
        for key in ["not_exhaustive_category_ids", "neg_category_ids"]:
            new_category_list = []
            for lvis_cat_id in image[key]:
                synset = lvis_cat_id_to_synset[lvis_cat_id]
                if synset not in synsets_to_keep:
                    continue
                coco_cat_id = synset_to_coco_cat_id[synset]
                new_category_list.append(coco_cat_id)
                coco_cat_id_with_instances[coco_cat_id] += 1
            image[key] = new_category_list
    coco_cat_id_with_instances = set(coco_cat_id_with_instances.keys())
    new_categories = []
    for cat in lvis_json["categories"]:
        synset = cat["synset"]
        if synset not in synsets_to_keep:
            continue
        coco_cat_id = synset_to_coco_cat_id[synset]
        if coco_cat_id not in coco_cat_id_with_instances:
            continue
        new_cat = copy.deepcopy(cat)
        new_cat["id"] = coco_cat_id
        new_categories.append(new_cat)
    cocofied_lvis["categories"] = new_categories
    with open(output_filename, "w") as f:
        json.dump(cocofied_lvis, f)
    print("{} is COCOfied and stored in {}.".format(input_filename, output_filename))