to_vect = Pipeline([('vect', CountVectorizer(min_df=2, max_df=0.9,
    ngram_range=(1, 1), max_features=100)), ('tfidf', TfidfTransformer())])
full_mapper = DataFrameMapper([('norm_text', to_vect), ('norm_fname', to_vect)]
    )
Using partial_fit with Scikit Pipeline