def classify(self, document, discrete=True):
        if self._root is None:
            self._train()
        return self._search(self._root, self._vector(document)[1])
Return a set of all keywords used in the corpus.
dataset/ETHPy150Open clips/pattern/pattern/vector/__init__.py/IGTree.classify--crossover with--dataset/ETHPy150Open nltk/nltk/nltk/corpus/reader/comparative_sents.py/ComparativeSentencesCorpusReader.keywords