I have a flex cable and don't know what it's for.

I have this flex cable right by the lcd and digitizer flex cable and it sticks out like this and I'm not sure what it's for. I bought a new chassis or midframe so i could replace my old one and it came with this cable. I turned it on without doing anything to it and leaving the back off, and the home button was not working. So I'm not sure if it's related to that or what.

Thanks