fn full_range_for(&self, duration_millis: u64) -> (u64, u64) {
        debug_assert!(self.ranges[0].0 == 0, "Ranges don't start at 0");

        for &(range_start, range_end) in self.ranges.iter().rev() {
            if duration_millis >= range_start {
                return (range_start, range_end);
            }
        }

        // First range starts from 0, and negative ranges are prohibited.
        unreachable!("Range for duration {} was not found", duration_millis);
    }
Returns the full time range for the provided duration.
core/tests/loadnext/src/report_collector/metrics_collector.rs