Migrating data from SQLiteOpenHelper base schema to DBFlow base schema

My app was using simple SQLiteOpenHelper database object and I was using its functions:

• onCreate => to create my schema

• onUpgrade => to change the schema when there is a change in db

Now I am shifting to DBFLOW orm and constructed almost new schema to further improve my app performance.

I have my scripts ready which will migrate the data from old schema to new schema, but I am missing some trigger points like onUpgrade since we only use FlowManager.init() for DBFlow.

How can we acheive this?