pub fn fork<A, B, C1, C2>(
cont1: PartialSession<C1, A>,
cont2: PartialSession<C2, B>,
) -> PartialSession<C1::Appended, SendChannel<A, B>>pub fn fork<A, B, C1, C2>(
cont1: PartialSession<C1, A>,
cont2: PartialSession<C2, B>,
) -> PartialSession<C1::Appended, SendChannel<A, B>>