How To Do CodeIgniter Form Validations Using Model

Hi friends,
As we have many rules available to validate form inputs in CodeIgniter v4.
Already we have an article over this topic,

I want to validate two table fields from a single model class file. Like Table A fields and Table B fields. From above article we can easily do with any specific table but not able to do with two tables.

Can anyone help me for this advance form validation concept.