def _stats(self, a):
        return (a / (a + 1.0),
                a / (a + 2.0) / (a + 1.0) ** 2,
                -2.0 * ((a - 1.0) / (a + 3.0)) * sqrt((a + 2.0) / a),
                6 * polyval([1, -1, -6, 2], a) / (a * (a + 3.0) * (a + 4)))
dataset/ETHPy150Open scipy/scipy/scipy/stats/_continuous_distns.py/powerlaw_gen._stats/original