def values(self):
        """
            Returns an iterator with each item being a stored value. The items
            are returned in order.
        """
        for v in self._items:
            if v is not None:
                yield v
        if self._upperitem is not None:
            yield self._upperitem

            Returns an iterator with each item being a stored value. The items
            are returned in order.
        
recipes/Python/457411_interval_mapping/recipe-457411.py