code: def _do_download(
          self, transport, file_obj, download_url, headers, start=None, end=None
      ):
          
          if self.chunk_size is None:
              download = Download(
                  download_url, stream=file_obj, headers=headers, start=start, end=end
              )
              download.consume(transport)
          else:
              download = ChunkedDownload(
                  download_url,
                  self.chunk_size,
                  file_obj,
                  headers=headers,
                  start=start if start else 0,
                  end=end,
              )
  
              while not download.finished:
                  download.consume_next_chunk(transport)
docs: Perform a download without any error handling.
  
          This is intended to be called by :meth:`download_to_file` so it can
          be wrapped with error handling / remapping.
  
          :type transport:
              :class:`~google.auth.transport.requests.AuthorizedSession`
          :param transport: The transport (with credentials) that will
                            make authenticated requests.
  
          :type file_obj: file
          :param file_obj: A file handle to which to write the blob's data.
  
          :type download_url: str
          :param download_url: The URL where the media can be accessed.
  
          :type headers: dict
          :param headers: Optional headers to be sent with the request(s).
  
          :type start: int
          :param start: Optional, the first byte in a range to be downloaded.
  
          :type end: int
          :param end: Optional, The last byte in a range to be downloaded.