docs: def save_boundaries_from_bounddict_ds9(bounddict, ds9_filename, numpix=100):
      """Export to ds9 region file the boundaries in bounddict.
  
      Parameters
      ----------
      bounddict : JSON structure
          Structure employed to store bounddict information.
      ds9_filename : str
          Output file name for the ds9 region file.
      numpix : int
          Number of points in which the X-range interval is subdivided
          in order to save each boundary as a connected set of line
          segments.
  
      """
  
      ds9_file = open(ds9_filename, 'w')
  
      ds9_file.write('# Region file format: DS9 version 4.1\n')
      ds9_file.write('global color=green dashlist=2 4 width=2 '
                     'font="helvetica 10 normal roman" select=1 '
                     'highlite=1 dash=1 fixed=0 edit=1 '
                     'move=1 delete=1 include=1 source=1\n')
      ds9_file.write('physical\n')
  
      uuid = bounddict['uuid']
      spfilter = bounddict['tags']['filter']
      grism = bounddict['tags']['grism']
  
      ds9_file.write('#\n# uuid (boundict file): {0}\n'.format(uuid))
      ds9_file.write('# filter..............: {0}\n'.format(spfilter))
      ds9_file.write('# grism...............: {0}\n'.format(grism))
  
      colorbox = ['green', 'green']
      for islitlet in range(1, EMIR_NBARS + 1):
          tmp_slitlet = 'slitlet' + str(islitlet).zfill(2)
          if tmp_slitlet in bounddict['contents'].keys():
              ds9_file.write('#\n# islitlet: {0}\n'.format(tmp_slitlet))
              read_dateobs = list(bounddict['contents'][tmp_slitlet].keys())
              read_dateobs.sort()
              for tmp_dateobs in read_dateobs:
                  ds9_file.write('#\n# date-obs: {0}\n'.format(tmp_dateobs))
                  tmp_dict = bounddict['contents'][tmp_slitlet][tmp_dateobs]
                  # lower boundary
                  pol_lower_measured = np.polynomial.Polynomial(
                      tmp_dict['boundary_coef_lower']
                  )
                  xmin_lower = tmp_dict['boundary_xmin_lower']
                  xmax_lower = tmp_dict['boundary_xmax_lower']
                  xdum = np.linspace(xmin_lower, xmax_lower, num=numpix)
                  ydum = pol_lower_measured(xdum)
                  for i in range(len(xdum) - 1):
                      ds9_file.write(
                          'line {0} {1} {2} {3}'.format(xdum[i], ydum[i],
                                                        xdum[i + 1], ydum[i + 1])
                      )
                      ds9_file.write(
                          ' # color={0}\n'.format(colorbox[islitlet % 2]))
                  # upper boundary
                  pol_upper_measured = np.polynomial.Polynomial(
                      tmp_dict['boundary_coef_upper']
                  )
                  xmin_upper = tmp_dict['boundary_xmin_upper']
                  xmax_upper = tmp_dict['boundary_xmax_upper']
                  xdum = np.linspace(xmin_upper, xmax_upper, num=numpix)
                  ydum = pol_upper_measured(xdum)
                  for i in range(len(xdum) - 1):
                      ds9_file.write(
                          'line {0} {1} {2} {3}'.format(xdum[i], ydum[i],
                                                        xdum[i + 1], ydum[i + 1])
                      )
                      ds9_file.write(
                          ' # color={0}\n'.format(colorbox[islitlet % 2]))
                  # slitlet label
                  xlabel = xmax_lower + xmax_upper + xmin_lower + xmin_upper
                  xlabel /= 4
                  yc_lower = pol_lower_measured(xlabel)
                  yc_upper = pol_upper_measured(xlabel)
                  ds9_file.write('text {0} {1} {{{2}}} # color={3} '
                                 'font="helvetica 10 bold '
                                 'roman"\n'.format(xlabel,
                                                   (yc_lower + yc_upper) / 2,
                                                   islitlet,
                                                   colorbox[islitlet % 2]))
  
      ds9_file.close()