Macro voice_flow 

macro_rules! voice_flow {
    (
        mod $module:ident {
            $( steps: [ $($step:ident),* $(,)? ]; )?
            $( tools: [ $($tool:ident),* $(,)? ]; )?
            $( slots: [ $($slot:ident),* $(,)? ]; )?
        }
    ) => { ... };
}

Generate a module of compile-time-checked flow name constants.

See the module docs for usage.