Yields binary chunks, respecting archive file headers and footers.

    Args:
      chunk: the StreamedFileChunk to be written

def _WriteFileChunk(self, chunk):
    """Yields binary chunks, respecting archive file headers and footers.

    Args:
      chunk: the StreamedFileChunk to be written
    """
    if chunk.chunk_index == 0:
      # Make sure size of the original file is passed. It's required
      # when output_writer is StreamingTarWriter.
      st = os.stat_result((0o644, 0, 0, 0, 0, 0, chunk.total_size, 0, 0, 0))
      target_path = _ClientPathToString(chunk.client_path, prefix=self.prefix)
      yield self.archive_generator.WriteFileHeader(target_path, st=st)

    yield self.archive_generator.WriteFileChunk(chunk.data)

    if chunk.chunk_index == chunk.total_chunks - 1:
      yield self.archive_generator.WriteFileFooter()
      self.archived_files.add(chunk.client_path)