def corofunc2():
            called[1] += 1
            return event.ReturnValue(insert_events=[evt3], append_events=[evt2])
def _cost_gp(self,x):
        """
        Predicts the time cost of evaluating the function at x.
        """
        m, _, _, _ = self.cost_model.predict_withGradients(x)
        return np.exp(m)