code: func secretsFunc(b *Brain, used, missing *dep.Set) func(string) ([]string, error) {
  	return func(s string) ([]string, error) {
  		var result []string
  
  		if len(s) == 0 {
  			return result, nil
  		}
  
  		d, err := dep.NewVaultListQuery(s)
  		if err != nil {
  			return nil, err
  		}
  
  		used.Add(d)
  
  		if value, ok := b.Recall(d); ok {
  			result = value.([]string)
  			return result, nil
  		}
  
  		missing.Add(d)
  
  		return result, nil
  	}
  }
docs: // secretsFunc returns or accumulates a list of secret dependencies from Vault.