Champion Select Screen Opt-Out Option

I'm on the champion select screen, what is the command line option to opt-out of this match? /leave /exit /quit (not the game; just the screen) Or, is there a button I need to click on without exiting the whole game?

Example: I'm on the Summoner's Rift Coop vs. AI champion select screen, I'm testing out a Top Lane champion, and someone else has already locked-in a Top Lane champion. At this point, I want to opt-out of this match, to let another willing person play, and to allow them to enjoy a Victory. I don't want to play a different champion with the hope that I might be able to choose my Top Lane champion in the next match. This match would be a waste my time. But, if I could opt-out, someone else can take my place, and we all would be happy.

Thank you.