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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def make_disk_kernel(radius, npix=501, cdelt=0.01, xpix=None, ypix=None):
 """Make kernel for a 2D disk. Parameters radius : float Disk radius in deg. """


    radius /= cdelt

    def fn(t, s): return 0.5 * (np.sign(s - t) + 1.0)

    dxy = make_pixel_distance(npix, xpix, ypix)
    k = fn(dxy, radius)
    k /= (np.sum(k) * np.radians(cdelt) ** 2)

    return k