Macro metric_catalog 

macro_rules! metric_catalog {
    (@kind Counter) => { ... };
    (@kind Gauge) => { ... };
    (@kind Histogram) => { ... };
    (@metadata $name:literal, $help:literal, $kind:ident) => { ... };
    ($($id:ident {
        name: $name:literal,
        help: $help:literal,
        kind: $kind:ident,
        samples: |$metrics:ident, $capture:ident, $output:ident| $samples:expr
    }),+ $(,)?) => { ... };
}