Specify a display hook that will be applied to objects of type
        objtype. The group specifies the set to which the display hook
        belongs, allowing the Store to compute the precedence within
        each group.

def set_display_hook(cls, group, objtype, hook):
        """
        Specify a display hook that will be applied to objects of type
        objtype. The group specifies the set to which the display hook
        belongs, allowing the Store to compute the precedence within
        each group.
        """
        cls._display_hooks[group][objtype] = hook