code: def get_url_and_headers_for_range(self, file_download):
          
          headers = self.get_range_headers()
          if file_download.http_headers:
              headers.update(file_download.http_headers)
          separator = ""
          if not file_download.url.startswith("/"):
              separator = "/"
          url = '{}{}{}'.format(file_download.host, separator, file_download.url)
          return url, headers
docs: Return url and headers to use for downloading part of a file, adding range headers.
          :param file_download: FileDownload: contains data about file we will download
          :return: str, dict: url to download and headers to use