PolyCont_FlatMap_Domain_MappedValue
given PolyCont_FlatMap_Domain_MappedValue[Upstream, UpstreamValue, Mapped, MappedValue, Domain](using val upstreamDsl: PolyCont[Upstream, Domain, UpstreamValue], val nestedDsl: PolyCont[Mapped, Domain, MappedValue]): PolyCont[FlatMap[Upstream, UpstreamValue, Mapped], Domain, MappedValue]