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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 nside_to_npix(nside):
 """ Find the number of pixels corresponding to a HEALPix resolution. Parameters nside : int The number of pixels on the side of one of the 12 'top-level' HEALPix tiles. Returns ------- npix : int The number of pixels in the HEALPix map. """

    nside = np.asanyarray(nside, dtype=np.int64)
    _validate_nside(nside)
    return 12 * nside ** 2