"Type Error: wpi.pcf8574Setup is not a function"

[Triadager]

Hey guys, I'm sorry to bother, but when I want to set up my PCF8574 I keep getting the error above. I'm really new to programming in general so I already put some hours into trying to figure out why it doesn't work but I just don't get it. What am I doing wrong? Or is this function not just not implemented yet?

var wpi = require("wiringpi-node");

wpi.pcf8574Setup(64,0x20);

The error occurs almost literally in the second line of my code. I'm running on "node.js" v8.6.0, "npm" version 5.4.2 and "wiringpi-node" version 2.4.4

I highly appreciate any help!

Thanks,

Flo