code: func validateMetaPair(key, value string, allowConsulPrefix bool) error {
  	if key == "" {
  		return fmt.Errorf("Key cannot be blank")
  	}
  	if !metaKeyFormat(key) {
  		return fmt.Errorf("Key contains invalid characters")
  	}
  	if len(key) > metaKeyMaxLength {
  		return fmt.Errorf("Key is too long (limit: %d characters)", metaKeyMaxLength)
  	}
  	if strings.HasPrefix(key, metaKeyReservedPrefix) && !allowConsulPrefix {
  		return fmt.Errorf("Key prefix '%s' is reserved for internal use", metaKeyReservedPrefix)
  	}
  	if len(value) > metaValueMaxLength {
  		return fmt.Errorf("Value is too long (limit: %d characters)", metaValueMaxLength)
  	}
  	return nil
  }
docs: // validateMetaPair checks that the given key/value pair is in a valid format