Macro create_slice 

macro_rules! create_slice {
    (
        enum_name: $enum_name:ident,
        fn_base: $base:ident,
        state: $state_ty:ty,
        initial_state: $initial_state:expr,
        actions: {
            $( $action_variant:ident $( { $($field:ident : $ftype:ty),* $(,)? } )? , )*
        },
        reducer: $reducer:expr
    ) => { ... };
}