title: Scikits-learn: Use custom vocabulary together with Pipeline
body: <p>In my scikits-learn Pipeline, I would like to pass a custom vocabulary to CountVectorizer():</p>
  
  <pre><code>text_classifier = Pipeline([
      ('count', CountVectorizer(vocabulary=myvocab)),
      ('tfidf', TfidfTransformer()),
      ('clf', LinearSVC(C=1000))
  ])
  </code></pre>
  
  <p>However, as far as I understand when I call</p>
  
  <pre><code>text_classifier.fit(X_train, y_train)
  </code></pre>
  
  <p>Pipeline uses the fit_transform() method of CountVectorizer(), which ignores myvocab. How could I modify my Pipeline to use myvocab? Thanks!</p>