pub trait RunCont<C, A> where
    C: Context,
    A: Protocol, {
    type Ret;
    fn run_cont(self, cont: PartialSession<C, A>) -> Self::Ret;
}pub trait RunCont<C, A> where
    C: Context,
    A: Protocol, {
    type Ret;
    fn run_cont(self, cont: PartialSession<C, A>) -> Self::Ret;
}