code: def _compute_acq_withGradients(self, x):
          
          m, s, dmdx, dsdx = self.model.predict_withGradients(x) 
          f_acqu = -m + self.exploration_weight * s       
          df_acqu = -dmdx + self.exploration_weight * dsdx
          return f_acqu, df_acqu
docs: Computes the GP-Lower Confidence Bound and its derivative