Does NLTK have TF-IDF implemented?

The NLTK TextCollection class has a method for computing the tf-idf of terms. The documentation is here, and the source is here. However, it says "may be slow to load", so using scikit-learn may be preferable.

I guess, there are enough evidences to conclude non-existence of TF-IDF in NLTK:

1. Unfortunately, calculating tf-idf is not available in NLTK so we'll use another data analysis library, scikit-learn

   from COMPSCI 290-01 Spring 2014 lab

2. More important, source code contains nothing related to tfidf (or tf-idf). Exceptions are NLTK-contrib, which contains map-reduce implementation for TF-IDF.

There are several libs for tf-idf mentioned in related question.

Upd: search by tf idf or tf_idf lets to find the function already found by @yvespeirsman