This method generates the classifier. This method assumes that the
        training data has been loaded

def train(self): 
        """
        This method generates the classifier. This method assumes that the
        training data has been loaded
        """
        if not self.training_data: 
            self.import_training_data()
        training_feature_set = [(self.extract_features(line), label) 
                                    for (line, label) in self.training_data]
        self.classifier = nltk.NaiveBayesClassifier.train(training_feature_set)