def accumulate(self, con_idx, csd_xy):
        denom = np.abs(csd_xy)
        z_denom = np.where(denom == 0.)
        denom[z_denom] = 1.
        this_acc = csd_xy / denom
        this_acc[z_denom] = 0.  # handle division by zero

        self._acc[con_idx] += this_acc
@Test: Generate a 4 group IPv4 address
dataset/ETHPy150Open mne-tools/mne-python/mne/connectivity/spectral.py/_PPCEst.accumulate--crossover with--dataset/ETHPy150Open omaciel/fauxfactory/tests/test_ipaddress.py/TestIpaddr.test_gen_ipv4_4