Macro create_exponential_histogram

macro_rules! create_exponential_histogram {
    (parent: $parent:expr, id: $id:expr, name: $name:expr, floor: $floor:expr,
        initial_step: $initial_step:expr, step_multiplier: $step_multiplier:expr,
        buckets: $buckets:expr, type: $type:ident) => { ... };
}