I am a newcomer to Prograph myself and barely know how to implement a simple mathematical formula.
Not widely available
As of Feb. 2021 Marten, a Prograph IDE designed for MacOS 10.6.8 through 10.15, is the only implementation I am aware of.
How to represent sample code
Rosettacode is well suited for programs that can easily be expressed as text, but Prograph programs are graphical. As far as I know, no mapping exists to represent Prograph as text. Mere images (“screenshots”) would be very limiting.