Macro define_function 

macro_rules! define_function {
    ($func_key:ident => {
        name: $fn_name:expr,
        documentation: $doc:expr,
        example: $example:expr,
        inputs: [$($input_name:ident: { documentation: $input_doc:expr, typing: $input_ts:expr $(, optional: $input_opt:expr)? }),*],
        output: { documentation: $output_doc:expr, typing: $output_ts:expr },
    }) => { ... };
}