PCF8574-transistor base switch

Hi @xreef, Thank you for this great library and all the effort you did. I am having difficulties to drive a transistor using the PCF8574 GPIO as a basic switch. My objective is to turn on and off audio lines using the bjt driven by the expender. I would like to request for sample/example schematic or circuit you use to connect a transistor to the expander. Thank you in advance