GPIO lines on RPi4

Hi All, does anyone have an example of how to control GOIO lines on the RPi4 from within a GRC flowgraph. I'm guessing it's an OOT module.

I need to generate a signal of a few 100Hz & control GPIO lines at various points though the cycle.

Alternatively, I could generate the signal & lines with external hardware & read them with GnuRadio.

Tnx, Dave