code: def format_progress(self, width):
          
          chunk_widths = self._get_chunk_sizes(width)
          progress_chunks = [chunk.format_chunk(chunk_width)
                             for (chunk, chunk_width)
                             in zip(self._progress_chunks, chunk_widths)]
          return "{sep_start}{progress}{sep_end}".format(
              sep_start=self.sep_start,
              progress="".join(progress_chunks),
              sep_end=self.sep_end
          )
docs: Create the formatted string that displays the progress.