<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def save_four_ds9(rectwv_coeff, debugplot=0):
 """Save the 4 possible ds9 region files. Parameters rectwv_coeff : RectWaveCoeff instance Rectification and wavelength calibration coefficients for the particular CSU configuration. debugplot : int Debugging level for messages and plots. For details see 'numina.array.display.pause_debugplot.py'. """


    for limits, rectified, suffix in zip(
        ['frontiers', 'frontiers', 'boundaries', 'boundaries'],
        [False, True, False, True],
        ['rawimage', 'rectified', 'rawimage', 'rectified']
    ):
        output = rectwv_coeff_to_ds9(rectwv_coeff=rectwv_coeff,
                                     limits=limits,
                                     rectified=rectified)
        filename = 'ds9_' + limits + '_' + suffix + '.reg'
        if abs(debugplot) >= 10:
            print('>>> Saving: ', filename)
        save_ds9(output, filename)