pub fn wait_session<I, P>(
session1: Session<End>,
cont: PartialSession<I, P>,
) -> PartialSession<I, P>where
P: Protocol,
I: Context + AppendContext<(End, ())> + AppendContext<(Empty, ())>,
I::Length: ContextLens<<I as AppendContext<(End, ())>>::Appended, End, Empty, Target = <I as AppendContext<(Empty, ())>>::Appended>,