code: func (m *metricMap) getMetricWithHashAndLabelValues(
  	h uint64, lvs []string, curry []curriedLabelValue,
  ) (Metric, bool) {
  	metrics, ok := m.metrics[h]
  	if ok {
  		if i := findMetricWithLabelValues(metrics, lvs, curry); i < len(metrics) {
  			return metrics[i].metric, true
  		}
  	}
  	return nil, false
  }
docs: // getMetricWithHashAndLabelValues gets a metric while handling possible
  // collisions in the hash space. Must be called while holding the read mutex.