Returns:
            Nx#class

def output_scores(self, name=None):
        """
        Returns:
            Nx#class
        """
        scores = [head.output_scores('cascade_scores_stage{}'.format(idx + 1))
                  for idx, head in enumerate(self._heads)]
        return tf.multiply(tf.add_n(scores), (1.0 / self.num_cascade_stages), name=name)