Function retrieve_table_names_by_labels 

async fn retrieve_table_names_by_labels(
    handler: &PrometheusHandlerRef,
    selectors: Vec<VectorSelector>,
    start: Option<&str>,
    end: Option<&str>,
    query_ctx: &QueryContextRef,
) -> Result<Vec<String>>

Resolves selectors constraining ordinary labels into metric names: the data answers the label matchers, then each selector’s __name__ matchers narrow the names it found.