title: Combine GridSearchCV and StackingClassifier
body: <p>I want to use StackingClassifier to combine some classifiers and then use GridSearchCV to optimize the parameters:</p>
  
  <pre><code>clf1 = RandomForestClassifier()
  clf2 = LogisticRegression()
  dt = DecisionTreeClassifier()
  sclf = StackingClassifier(estimators=[clf1, clf2],final_estimator=dt)
  
  params = {'randomforestclassifier__n_estimators': [10, 50],
            'logisticregression__C': [1,2,3]}
  
  grid = GridSearchCV(estimator=sclf, param_grid=params, cv=5)
  
  grid.fit(x, y)
  
  </code></pre>
  
  <p>But this turns out an error:</p>
  
  <pre><code>'RandomForestClassifier' object has no attribute 'estimators_'
  </code></pre>
  
  <p>I have used <code>n_estimators</code>. Why it warns me that no <code>estimators_</code>?</p>
  
  <p>Usually GridSearchCV is applied to single model so I just need to write the name of parameters of the single model in a dict.</p>
  
  <p>I refer to this page <a href="https://groups.google.com/d/topic/mlxtend/5GhZNwgmtSg" rel="noreferrer">https://groups.google.com/d/topic/mlxtend/5GhZNwgmtSg</a> but it uses parameters of early version. Even though I change the newly parameters it doesn't work.  </p>
  
  <p>Btw, where can I learn the details of the naming rule of these params?</p>