title: How to get best estimator parameters using AdaBoost and GridSearchCV
body: <p>I'm using <code>AdaBoost</code> and I'd like to see which estimator parameters work best using <code>GridSearchCV</code>. Is it possible to include the estimator parameters in my 'parameters' variable? For instance, how can I vary the max_depth for the DecisionTreeClassifier?</p>
  
  <pre><code>pipe = Pipeline([
               ('normalize', MinMaxScaler(feature_range=(0, 1))),
               ('scale', StandardScaler()),
               ('booster', AdaBoostClassifier()),
               ])
  
  parameters = {
          "booster__base_estimator": [DecisionTreeClassifier(), RandomForestClassifier(n_estimators=20)],
          "booster__n_estimators": [20, 30, 40],
          "booster__learning_rate": [0.1, 0.5, 1]
       }
  </code></pre>