How to use the parfive.utils.get_http_size function in parfive

if 'HTTP_PROXY' in os.environ and scheme == 'http':
                kwargs['proxy'] = os.environ['HTTP_PROXY']
            elif 'HTTPS_PROXY' in os.environ and scheme == 'https':
                kwargs['proxy'] = os.environ['HTTPS_PROXY']

            async with session.get(url, timeout=timeout, **kwargs) as resp:
                if resp.status != 200:
                    raise FailedDownload(filepath_partial, url, resp)
                else:
                    filepath, skip = get_filepath(filepath_partial(resp, url), overwrite)
                    if skip:
                        return str(filepath)
                    if callable(file_pb):
                        file_pb = file_pb(position=token.n, unit='B', unit_scale=True,
                                          desc=filepath.name, leave=False,
                                          total=get_http_size(resp))
                    else:
                        file_pb = None

                    # This queue will contain the downloaded chunks and their offsets
                    # as tuples: (offset, chunk)
                    downloaded_chunk_queue = asyncio.Queue()

                    download_workers = []
                    writer = self.loop.create_task(
                        self._write_worker(downloaded_chunk_queue, file_pb, filepath))

                    if max_splits and resp.headers.get('Accept-Ranges', None) == "bytes":
                        content_length = int(resp.headers['Content-length'])
                        split_length = content_length // max_splits
                        ranges = [
                            [start, start + split_length]