packageengineimport("time""github.com/ethereum-optimism/optimism/op-service/eth")typeBuildStartedEventstruct{Infoeth.PayloadInfoBuildStartedtime.TimeParenteth.L2BlockRef// if payload should be promoted to safe (must also be pending safe, see DerivedFrom)IsLastInSpanbool// payload is promoted to pending-safe if non-zeroDerivedFrometh.L1BlockRef}func(evBuildStartedEvent)String()string{return"build-started"}func(eq*EngDeriver)onBuildStarted(evBuildStartedEvent){// If a (pending) safe block, immediately seal the blockifev.DerivedFrom!=(eth.L1BlockRef{}){eq.emitter.Emit(BuildSealEvent{Info:ev.Info,BuildStarted:ev.BuildStarted,IsLastInSpan:ev.IsLastInSpan,DerivedFrom:ev.DerivedFrom,})}}