'Train the classifier with a labeled and unlabeled feature sets and return
the classifier. Takes the same arguments as the wrapped NLTK class.
This method is implicitly called when calling ``classify`` or
``accuracy`` methods and is included only to allow passing in arguments
to the ``train`` method of the wrapped NLTK class.
:rtype: A classifier'

def train(self, *args, **kwargs):

    self.classifier = self.nltk_class.train(self.positive_features, self.unlabeled_features, self.positive_prob_prior)
    return self.classifier
