Return all instances that inherit from JB_Gui

        :returns: all instances that inherit from JB_Gui
        :rtype: list
        :raises: None

def allinstances(cls):
        """Return all instances that inherit from JB_Gui

        :returns: all instances that inherit from JB_Gui
        :rtype: list
        :raises: None
        """
        JB_Gui._allinstances = weakref.WeakSet([i for i in cls._allinstances if shiboken.isValid(i)])
        return list(cls._allinstances)