models.arrow: fix docs.
models.arrow: fix docs.

mrjbq7/factor,factor/factor,bpollack/factor,tgunr/factor,tgunr/factor,bpollack/factor,mrjbq7/factor,mrjbq7/factor,bpollack/factor,factor/factor,bpollack/factor,bpollack/factor,factor/factor,factor/factor,tgunr/factor,mrjbq7/factor,tgunr/factor,bpollack/factor,bpollack/factor,factor/factor,factor/factor,mrjbq7/factor,tgunr/factor,tgunr/factor,mrjbq7/factor