docs: def import_training_data(self,
              positive_corpus_file=os.path.join(os.path.dirname(__file__),
                  "positive.txt"),
              negative_corpus_file=os.path.join(os.path.dirname(__file__),
                  "negative.txt")
              ):
          """
          This method imports the positive and negative training data from the
          two corpus files and creates the training data list. 
          """
  
          positive_corpus = open(positive_corpus_file)
          negative_corpus = open(negative_corpus_file)
  
          # for line in positive_corpus: 
          #     self.training_data.append((line, True))
  
          # for line in negative_corpus: 
          #     self.training_data.append((line, False))
  
          # The following code works. Need to profile this to see if this is an
          # improvement over the code above. 
          positive_training_data = list(map(lambda x: (x, True), positive_corpus))
          negative_training_data = list(map(lambda x: (x, False), negative_corpus))
          self.training_data = positive_training_data + negative_training_data