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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 _neighbour_pixels(hp, ipix):
 """ Returns all the pixels neighbours of ``ipix`` """

        neigh_ipix = np.unique(hp.neighbours(ipix).ravel())
        # Remove negative pixel values returned by `~astropy_healpix.HEALPix.neighbours`
        return neigh_ipix[np.where(neigh_ipix >= 0)]