docs: def overplot_lines(ax,
                     catlines_all_wave,
                     list_valid_islitlets,
                     rectwv_coeff,
                     global_integer_offset_x_pix, global_integer_offset_y_pix,
                     ds9_file, debugplot):
      """Overplot lines (arc/OH).
  
      Parameters
      ----------
      ax : matplotlib axes
          Current plot axes.
      catlines_all_wave : numpy array
          Array with wavelengths of the lines to be overplotted.
      list_valid_islitlets : list of integers
          List with numbers of valid slitlets.
      rectwv_coeff : RectWaveCoeff instance
          Rectification and wavelength calibration coefficients for the
          particular CSU configuration.
      global_integer_offset_x_pix : int
          Global offset in the X direction to be applied after computing
          the expected location.
      global_integer_offset_y_pix : int
          Global offset in the Y direction to be applied after computing
          the expected location.
      ds9_file : file handler or None
          File handler to ds9 region file where the location of lines
          must be saved.
      debugplot : int
          Debugging level for messages and plots. For details see
          'numina.array.display.pause_debugplot.py'.
  
      """
  
      for islitlet in list_valid_islitlets:
          crval1_linear = rectwv_coeff.contents[islitlet - 1]['crval1_linear']
          cdelt1_linear = rectwv_coeff.contents[islitlet - 1]['cdelt1_linear']
          crvaln_linear = crval1_linear + (EMIR_NAXIS1 - 1) * cdelt1_linear
          bb_ns1_orig = rectwv_coeff.contents[islitlet - 1]['bb_ns1_orig']
          ttd_order = rectwv_coeff.contents[islitlet - 1]['ttd_order']
          aij = rectwv_coeff.contents[islitlet - 1]['ttd_aij']
          bij = rectwv_coeff.contents[islitlet - 1]['ttd_bij']
          min_row_rectified = float(
              rectwv_coeff.contents[islitlet - 1]['min_row_rectified']
          )
          max_row_rectified = float(
              rectwv_coeff.contents[islitlet - 1]['max_row_rectified']
          )
          mean_row_rectified = (min_row_rectified + max_row_rectified) / 2
          wpoly_coeff = rectwv_coeff.contents[islitlet - 1]['wpoly_coeff']
          x0 = []
          y0 = []
          x1 = []
          y1 = []
          x2 = []
          y2 = []
          for line in catlines_all_wave:
              if crval1_linear <= line <= crvaln_linear:
                  tmp_coeff = np.copy(wpoly_coeff)
                  tmp_coeff[0] -= line
                  tmp_xroots = np.polynomial.Polynomial(tmp_coeff).roots()
                  for dum in tmp_xroots:
                      if np.isreal(dum):
                          dum = dum.real
                          if 1 <= dum <= EMIR_NAXIS1:
                              x0.append(dum)
                              y0.append(mean_row_rectified)
                              x1.append(dum)
                              y1.append(min_row_rectified)
                              x2.append(dum)
                              y2.append(max_row_rectified)
          xx0, yy0 = fmap(ttd_order, aij, bij, np.array(x0), np.array(y0))
          xx0 -= global_integer_offset_x_pix
          yy0 += bb_ns1_orig
          yy0 -= global_integer_offset_y_pix
          xx1, yy1 = fmap(ttd_order, aij, bij, np.array(x1), np.array(y1))
          xx1 -= global_integer_offset_x_pix
          yy1 += bb_ns1_orig
          yy1 -= global_integer_offset_y_pix
          xx2, yy2 = fmap(ttd_order, aij, bij, np.array(x2), np.array(y2))
          xx2 -= global_integer_offset_x_pix
          yy2 += bb_ns1_orig
          yy2 -= global_integer_offset_y_pix
  
          if abs(debugplot) % 10 != 0:
              if abs(debugplot) == 22:
                  for xx1_, xx2_, yy1_, yy2_ in zip(xx1, xx2, yy1, yy2):
                      ax.plot([xx1_, xx2_], [yy1_, yy2_], 'c-', linewidth=2.0)
              else:
                  ax.plot(xx0, yy0, 'c.')
  
          if ds9_file is not None:
              ds9_file.write(
                  '#\n# islitlet...........: {0}\n'.format(islitlet)
              )
              for xx0_, yy0_ in zip(xx0, yy0):
                  ds9_file.write(
                      'circle {0} {1} 2 # fill=1\n'.format(
                          xx0_, yy0_)
                  )