// and value.String() for the flag's value.
func CountFlagValue(prefix string, flagSet flag.FlagSet, flagName string) {
	// TODO(matloob): Maybe pass in a list of flagNames if we end up counting
	// values for more than one?
	// TODO(matloob): Add this to x/telemetry?
	flagSet.Visit(func(f *flag.Flag) {
		if f.Name == flagName {
			counter.New(prefix + f.Name + ":" + f.Value.String()).Inc()
		}
	})
}

// A label overwrites a prior label with the same key.
func WithLabels(ctx context.Context, labels LabelSet) context.Context {
	parentLabels := labelValue(ctx)
	childLabels := make(labelMap, len(parentLabels))
	// TODO(matloob): replace the map implementation with something
	// more efficient so creating a child context WithLabels doesn't need
	// to clone the map.
	for k, v := range parentLabels {
		childLabels[k] = v
	}