Macro wdf_compose 

macro_rules! wdf_compose {
    (
        name: $name:ident<T>,
        kind: Series,
        elements: ($left:ty, $right:ty),
    ) => { ... };
    (
        name: $name:ident<T>,
        kind: Parallel,
        elements: ($left:ty, $right:ty),
    ) => { ... };
}

Compose two WDF elements into Series or Parallel.