How to override behaviour of AddIndexConcurrently in Django?

The AddIndexConcurrently django class does the following SQL:

CREATE INDEX CONCURRENTLY <idx_name>

However, I have an application that requires something a bit more complex.
I.e., I need to do some checks on the table, and if those checks pass I need to run

CREATE INDEX CONCURRENTLY IF NOT EXISTS <idx_name>

Is there a way to do that so that I can just override AddIndexConcurrently with my own class and do what I need to do there?

/r/django
https://redd.it/1c5xvbf