ObjCellViewVarImpl
abstract class ObjCellViewVarImpl[T <: Txn[T], Dur <: ([~ <: Txn[~]] =>> Obj[~]), In <: Obj { type Peer <: ([~ <: Txn[~]] =>> Dur[~]); }](h: Source[T, Obj[T]], key: String)(implicit ct: ClassTag[Dur[T]], context: Context[T]) extends Var[T, Option[In]]