Macro register 

macro_rules! register {
    (
        $(layers: [$( $layer_type:ty ),* ])?$(,)?
        $(acts: [$( $activation_type:ty ),* ])?$(,)?
        $(costs: [$( $cost_type:ty ),* ])?$(,)?
    ) => { ... };
}

Macro to register your own layers, activations and costs