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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 refine_aseg(aseg, ball_size=4):
 """ First step to reconcile ANTs' and FreeSurfer's brain masks. Here, the ``aseg.mgz`` mask from FreeSurfer is refined in two steps, using binary morphological operations: 1. With a binary closing operation the sulci are included into the mask. This results in a smoother brain mask that does not exclude deep, wide sulci. 2. Fill any holes (typically, there could be a hole next to the pineal gland and the corpora quadrigemina if the great cerebral brain is segmented out). """

    # Read aseg data
    bmask = aseg.copy()
    bmask[bmask > 0] = 1
    bmask = bmask.astype(np.uint8)

    # Morphological operations
    selem = sim.ball(ball_size)
    newmask = sim.binary_closing(bmask, selem)
    newmask = binary_fill_holes(newmask.astype(np.uint8), selem).astype(np.uint8)

    return newmask.astype(np.uint8)