Methods to work with `json_tree` representation: load/dump from/to a directory.
load_json_tree(tree_dir:Union[str, Path], kind:str='object_detection')
dump_json_tree(coco:CocoDataset, target_dir:Union[str, Path], kind:str='object_detection', skip_nulls:bool=True, overwrite:bool=False, indent:Optional[int]=4)