Args for Engine.drainEffects — the drainer's identity is the engine client's token, like every other verb.
Optional
Restrict to specific effect names. At least one name; an empty list throws. Omitted considers every claimable entry, including ones no handler covers, which missingHandler then decides.
missingHandler
Args for Engine.drainEffects — the drainer's identity is the engine client's token, like every other verb.