def moment(x, n, axis=None):
    return (((x - x.mean(axis=axis, keepdims=True)) ** n).sum(axis=axis) / np.ones_like(x).sum(axis=axis))
def moment(x, n, axis=None):
    return (((x - x.mean(axis=axis, keepdims=True)) ** n).sum(axis=axis) / np.ones_like(x).sum(axis=axis))