Function create_metric 

pub fn create_metric<T: PrometheusMetric, H: MetricsHierarchy + ?Sized>(
    hierarchy: &H,
    metric_name: &str,
    metric_desc: &str,
    labels: &[(&str, &str)],
    buckets: Option<Vec<f64>>,
    const_labels: Option<&[&str]>,
) -> Result<T>

============================== Metrics section

Public helper function to create metrics - accessible for Python bindings