docs: def _write_sys_header(self, sys_header):
          """
          See src/pipematt/step3matt-c
          """
          header_vals = [sys_header[RMIN], sys_header[RMAX], sys_header[ANGLE],
                         sys_header[AWIDTH]]
          self._write_line("##     RMIN    RMAX   ANGLE   AWIDTH")
          self._write_line("# %8.1f%8.1f%8.1f%8.1f" % tuple(map(float, header_vals)))