Macro tx_schema 

macro_rules! tx_schema {
    (
        $name:ident,
        keys: [ $($key:ident),* $(,)? ],
        params: { $($param_field:ident: $param_type:ty),* $(,)? },
        state: { $($state_field:ident: $state_type:ty),* $(,)? }
        $(,)?
    ) => { ... };
}