code: func parseGracePeriods(statements map[string]string) (map[evictionapi.Signal]time.Duration, error) {
  	if len(statements) == 0 {
  		return nil, nil
  	}
  	results := map[evictionapi.Signal]time.Duration{}
  	for signal, val := range statements {
  		signal := evictionapi.Signal(signal)
  		if !validSignal(signal) {
  			return nil, fmt.Errorf(unsupportedEvictionSignal, signal)
  		}
  		gracePeriod, err := time.ParseDuration(val)
  		if err != nil {
  			return nil, err
  		}
  		if gracePeriod < 0 {
  			return nil, fmt.Errorf("invalid eviction grace period specified: %v, must be a positive value", val)
  		}
  		results[signal] = gracePeriod
  	}
  	return results, nil
  }
docs: // parseGracePeriods parses the grace period statements