def get_max_num(self, request, obj=None, **kwargs):
        max_num = 3
        if obj:
            return max_num + obj.binarytree_set.count()
        return max_num


# admin for #19524
dataset/ETHPy150Open django/django/tests/admin_inlines/admin.py/BinaryTreeAdmin.get_max_num/operator `-` -> `+`