RateLimiter in source code - how to configure

Hey, in the sourcecode I can find a rate limiter. But I found no documentation how to configure and what it exactly does.
And does it act like a normal rate limiter or it is something else, because the struct I found has not the normal options I would expect: dgraph/x.go at 9e8200945e66eff96786a1f0e9fb1e435c4be4e0 · dgraph-io/dgraph · GitHub

Hi @ngladbach
Check this out: