Thank you for noticing that the set_interrupt_polarity() function is not in the documentation.
set_interrupt_polarity(polarity) allows you to set the polarity of the two interrupt pins INTA and INTB so they go either high or low when active.
The function takes a single parameter of 0 or 1. 0 = Active Low, 1 = Active High
I have added the function into the documentation for the IO Pi and Expander Pi which you can find on our GitHub python repository at https://github.com/abelectronicsuk/ABElectronics_Python_Libraries