docs: def _fold_line(self, line):
          """Write string line as one or more folded lines."""
          if len(line) <= self._cols:
              self._output_file.write(line)
              self._output_file.write(self._line_sep)
          else:
              pos = self._cols
              self._output_file.write(line[0:self._cols])
              self._output_file.write(self._line_sep)
              while pos < len(line):
                  self._output_file.write(b' ')
                  end = min(len(line), pos + self._cols - 1)
                  self._output_file.write(line[pos:end])
                  self._output_file.write(self._line_sep)
                  pos = end