'Build a new classifier, based on the given training data
*tagged_corpus*.'

def _train(self, tagged_corpus, classifier_builder, verbose):

    classifier_corpus = []
    if verbose:
        print(u'Constructing    training    corpus    for    classifier.')
    for sentence in tagged_corpus:
        history = []
        (untagged_sentence, tags) = zip(*sentence)
        for index in range(len(sentence)):
            featureset = self.feature_detector(untagged_sentence, index, history)
            classifier_corpus.append((featureset, tags[index]))
            history.append(tags[index])
    if verbose:
        print((u'Training    classifier    (%d    instances)' % len(classifier_corpus)))
    self._classifier = classifier_builder(classifier_corpus)
