code: def format_sklearn(self):
          
          X, y = zip(*self.get_labeled_entries())
          return np.array(X), np.array(y)
docs: Returns dataset in (X, y) format for use in scikit-learn.
          Unlabeled entries are ignored.
  
          Returns
          -------
          X : numpy array, shape = (n_samples, n_features)
              Sample feature set.
  
          y : numpy array, shape = (n_samples)
              Sample labels.