Custom predicates for blocking

[lcpprop]

I have a really large dataset > 750 000 rows. I want to create a custom predicate where columns1 and columns3 should be the same across comparison pairs.

I could define them as such using dedupe predicate classes:

predicates.CompoundPredicate([
predicates.wholeFieldPredicate('pltr_gross_amt'),
predicates.wholeFieldPredicate('pltr_tran_date')
])

Now, how do I implement my custom predicate, such that all uncertain rows that are shown would adhere to this predicate? Could I overwrite default predicates?