'Update the concentration parameters for each cluster'

def _update_concentration(self, z):

    sz = np.sum(z, axis=0)
    self.gamma_.T[1] = (1.0 + sz)
    self.gamma_.T[2].fill(0)
    for i in range((self.n_components - 2), (-1), (-1)):
        self.gamma_[(i, 2)] = (self.gamma_[((i + 1), 2)] + sz[i])
    self.gamma_.T[2] += self.alpha
