'More precise calculation than log(sf)'

def _logsf(self, k, M, n, N):

    res = []
    for (quant, tot, good, draw) in zip(k, M, n, N):
        k2 = np.arange((quant + 1), (draw + 1))
        res.append(logsumexp(self._logpmf(k2, tot, good, draw)))
    return np.asarray(res)
