Fix for beta channel (collections are unstable)
Fix for beta channel (collections are unstable)

spazm/xrust,spazm/xrust,ekse/exercism-rust,stevejb71/xrust,exercism/xrust,medek/xrust,sacherjj/rust,stevejb71/xrust,petertseng/exercism-rust,petertseng/exercism-rust,petertseng/exercism-rust,Jeff-Hostetler/xrust,sacherjj/rust,sacherjj/rust,ekse/exercism-rust,pminten/xrust,medek/xrust,Jeff-Hostetler/xrust,pminten/xrust,exercism/xrust