docs: def add(self, key, value,
              description='',
              history_max_size=None):
          """Add an new item (key, value) to the current history."""
          if key not in self.stats_history:
              self.stats_history[key] = GlancesAttribute(key,
                                                         description=description,
                                                         history_max_size=history_max_size)
          self.stats_history[key].value = value