def METHOD_NAME(self, dt):
    if self.havec:
        self.x0 = EXOSIMS.util.KeplerSTM_C.CyKeplerSTM.CyKeplerSTM(
            self.x0, dt, self.mu, self.epsmult
        )
    else:
        tmp = np.zeros(self.x0.shape)
        for j in range(self.nplanets):
            Phi = self.calcSTM(dt, j)
            tmp[j * 6 : (j + 1) * 6] = np.dot(Phi, self.x0[j * 6 : (j + 1) * 6])
        self.updateState(tmp)