.feature_names))
        s_background=qsample(NULLSTR,modelneg,steps=nullsteps)
        explainer = shap.KernelExplainer(funcw_,np.array([s_background]))
        shap_values = explainer.shap_values(X[:shapnum])
        
        self.shap_index=pd.DataFrame(shap_values.mean(axis=0),
                                     columns=[&#39;shap&#39;])\
                          .sort_values(&#39;shap&#39;,
                                       ascending=False).index.values
        
        modelneg.shap_index=self