You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: macros.rs
    path of file: ./repos/metrics/metrics/src
    
    the code of the file until where you have to start completion: #[doc(hidden)]
#[macro_export]
macro_rules! metadata_var {
    ($target:expr, $level:expr) => {{
        static METADATA: $crate::Metadata<'static> = $crate::Metadata::new(
            $target,
        
    
/// # fn main() {
/// // A basic gauge:
/// let gauge = gauge!("some_metric_name");
/// gauge.increment(1.0);
///
/// // Specifying labels inline, including using constants for either the key or value:
/// let gauge = gauge!("some_metric_name", "service" => "http");
/// gauge.decrement(42.0);
///
/// const SERVICE_LABEL: &'static str = "service";
/// const SERVICE_HTTP: &'static str = "http";
/// let gauge = gauge!("some_metric_name", SERVICE_LABEL => SERVICE_HTTP);
/// gauge.increment(3.14);
///
/// // We can also pass labels by giving a vector or slice of key/value pairs.  In this scenario,
/// // a unit or description can still be passed in their respective positions:
/// let dynamic_val = "woo";
/// let labels = [("dynamic_key", format!("{}!", dynamic_val))];
/// let gauge = gauge!("some_metric_name", &labels);
/// gauge.set(1337.0);
///
/// // As mentioned in the documentation, metric names also can be owned strings, including ones
/// // generated at the callsite via things like `format!`:
/// let name = String::from("some_owned_metric_name");
/// let gauge = gauge!(name);
///
/// let gauge = gauge!(format!("{}_via_format", "name"));
/// # }