I am working on a project which uses Mageplaza Layered Navigation. I need to change the behavior of multiselect from OR to AND.

As an example, I create attribute color. When I search for red and black, it should only show products that are red AND black not all the products which have red OR black.

Multiselect is correctly set, the only problem is to change the code - I cannot find where should I change. And what the code to change. If anyone has the code or updated extension meets the upper condition please share.