def on_checked_changed(self, group, checked_id):
        """ Set the checked property based on the checked state
        of all the children
        
        """
        d = self.declaration
        if checked_id < 0:
            with self.widget.clearCheck.suppressed():
                d.checked = None
            return
        else:
            for c in self.children():
                if c.widget.getId() == checked_id:
                    with self.widget.check.suppressed():
                        d.checked = c.declaration
                    return
Set the checked property based on the checked state
        of all the children