How to use the parfive.Downloader function in parfive

def main():
    args = parse_args(sys.argv[1:])
    downloader = Downloader(max_conn=args.max_conn, file_progress=not args.no_file_progress, overwrite=args.overwrite)
    for url in args.urls:
        downloader.enqueue_file(url, path=args.directory)
    results = downloader.download()
    for i in results:
        print(i)

    err_str = ''
    for err in results.errors:
        err_str += f'{err.url} \t {err.exception}\n'
    if err_str:
        sys.exit(err_str)

def getenvironment(self):
        try:
            from parfive import Downloader
        except ImportError:
            log.error("To use gammapy download, install the parfive package!")
            return

        dl = Downloader(progress=False, file_progress=False)
        filename_env = "gammapy-" + self.release + "-environment.yml"
        url_file_env = RELEASES_BASE_URL + "/install/" + filename_env
        filepath_env = str(self.outfolder / filename_env)
        dl.enqueue_file(url_file_env, path=filepath_env)
        try:
            log.info(f"Downloading {url_file_env}")
            Path(filepath_env).parent.mkdir(parents=True, exist_ok=True)
            dl.download()
        except Exception as ex:
            log.error(ex)
            exit()

def run(self):
        try:
            from parfive import Downloader
        except ImportError:
            log.error("To use gammapy download, install the parfive package!")
            return

        if self.listfiles:
            log.info(f"Content will be downloaded in {self.outfolder}")

        dl = Downloader(progress=self.progress, file_progress=False)
        for rec in self.listfiles:
            url = self.listfiles[rec]["url"]
            path = self.outfolder / self.listfiles[rec]["path"]
            md5 = ""
            if "hashmd5" in self.listfiles[rec]:
                md5 = self.listfiles[rec]["hashmd5"]
            retrieve = True
            if md5 and path.exists():
                md5local = hashlib.md5(path.read_bytes()).hexdigest()
                if md5local == md5:
                    retrieve = False
            if retrieve:
                dl.enqueue_file(url, path=str(path.parent))

        log.info(f"{dl.queued_downloads} files to download.")
        res = dl.download()