title: YellowbrickTypeError: could not find feature importances param on Pipeline
body: <p>I'm getting this error when calling</p>
  <pre><code>    viz = feature_importances(model_lr, X_train, y_train, labels=final_features, topn=20, is_fitted=True, ax=axes[1,0], show=False)
  </code></pre>
  <p>Here is how the pipeline is setup:</p>
  <pre><code>        clf_lr = Pipeline(
      steps=[(&quot;preprocessor&quot;, preprocessor), 
             (&quot;feature_selector&quot;, RFE(estimator=RandomForestClassifier(random_state=42), verbose=3, n_features_to_select=15)) ,
             (&quot;classifier&quot;, LogisticRegression(max_iter=3000, random_state=42)),
            ] 
  )
  
  gs_lr     = GridSearchCV(clf_lr, 
                           lr_param_grid, #some param grid for lr, omitted her
                           cv=cv,
                           scoring={'bsl': bsl_scorer}, 
                           verbose=3, 
                           error_score='raise',
                           n_jobs=-1,
                           refit='bsl')
  model_lr    = gs_lr.fit(X_train, y_train)
  </code></pre>