code: def __set_labels(self, labels):
          
          with self.fs.open(self.fs.join(self.path, self.LABEL_FILE), 'w') \
                  as file_desc:
              for label in labels:
                  file_desc.write("%s,%s\n" % (label.name,
                                               label.get_color_str()))
docs: Add a label on the document.