def METHOD_NAME(self, pcliq, pcice, si):
    sstar =  self.wrm.saturation(pcliq)
    tmp = (1.0 - si) * sstar
    G1 = self.wrm.d_saturation( pcice + self.wrm.capillaryPressure( tmp + si))
    G2 = self.wrm.d_capillaryPressure( tmp + si )
    return -G1 / (sstar + G1*G2*(1-sstar))