Update csst_ifs_gehong/config.py, tests/test_cube3d.py

        Pixel size in the spatial direction, by default 0.2arcsec

    """

    def __init__(self, wave_min = 3500.0, wave_max = 10000.0, 

                 dlam = 1.0, inst_fwhm = 0.1,

                 nx = 100, ny = 100, dpix = 0.1):

                 dlam = 2.0, inst_fwhm = 0.1,

                 nx = 30, ny = 30, dpix = 0.2):

        self.dlam = dlam

        self.wave = np.arange(wave_min, wave_max, dlam)

        self.wave_min = wave_min

        u.savefits('result.fits')

        if np.sum(u.flux[50,50,:]) != np.sum(u.flux[5,95,:]):

        if np.sum(u.flux[15,15,:]) != np.sum(u.flux[5,25,:]):

            print("No Problem!")

        #plt.figure(figsize=(16,4))