@classmethod
def _decr_instances(cls, instance):
    """
        Remove from list and reposition other bars
        so that newer bars won't overlap previous bars
        """
    try:
        cls._instances.remove(instance)
        for inst in cls._instances:
            if inst.pos > instance.pos:
                inst.pos -= 1
        if not cls._instances and cls.monitor:
            cls.monitor.exit()
            del cls.monitor
            cls.monitor = None
    except KeyError:
        pass
