Need to restrict few tasks in Project Module for my custom group named customers

For example if my project name is "CAFR". I have 50 tasks and only 20 tasks should be visible to my custom group named customers.

created a new record rule as ['&',('wbs_private','=',False),('project_id.user_id','=',False)] but it is not working.

Wbs_private is my boolean field to check the status.

Any inputs please