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