vocabs.hierarchy: ensure-valid-root only once per root.
vocabs.hierarchy: ensure-valid-root only once per root.

bpollack/factor,factor/factor,mrjbq7/factor,bjourne/factor,slavapestov/factor,slavapestov/factor,nicolas-p/factor,sarvex/factor-lang,bjourne/factor,factor/factor,bpollack/factor,AlexIljin/factor,AlexIljin/factor,nicolas-p/factor,AlexIljin/factor,bpollack/factor,sarvex/factor-lang,mrjbq7/factor,mrjbq7/factor,mrjbq7/factor,factor/factor,mrjbq7/factor,dch/factor,AlexIljin/factor,bpollack/factor,nicolas-p/factor,dch/factor,tgunr/factor,nicolas-p/factor,bjourne/factor,sarvex/factor-lang,sarvex/factor-lang,nicolas-p/factor,dch/factor,bpollack/factor,dch/factor,nicolas-p/factor,AlexIljin/factor,bpollack/factor,factor/factor,bjourne/factor,factor/factor,slavapestov/factor,bjourne/factor,tgunr/factor,bjourne/factor,slavapestov/factor,slavapestov/factor,AlexIljin/factor,dch/factor,bpollack/factor,mrjbq7/factor,sarvex/factor-lang,sarvex/factor-lang,slavapestov/factor,bjourne/factor,dch/factor,slavapestov/factor,sarvex/factor-lang,tgunr/factor,tgunr/factor,factor/factor,nicolas-p/factor,AlexIljin/factor,tgunr/factor,tgunr/factor