MathBuster09

Hey, I've been trying at this for hours now, I keep getting errors. I want to make the player get teleported back if they are not holding a piece of paper named "&bCourse Key 1" after they walk on glass. on step on glass: set {_key1} to paper named "&bCourse Key 1" [living entities] isn't holding teleport player to (307, 4, -184, world) I get 1 error, I does not understand line 3, thanks to anyone who can help!