@rout HTML, PHP Or JS ?

Question

I Was Watching A Tutorial About Server Side Testing For Networking In Python The Example Server Code Is Downloadable But When I Opened It I Saw That It's A Web Page Contains A Function That I Never Saw Called @rout like Does HTML, JS or PHP Has Any Function Like This What I Know About This Function Or Statement That It Requests A Permission For Using The Router So Which Language Of These Has This Function ?

Answer 1

JS

Answer 2

@Hennry Php Provides That Too