code: func checkRegionForParsing(numberToParse, defaultRegion string) bool {
  	if !isValidRegionCode(defaultRegion) {
  		// If the number is null or empty, we can't infer the region.
  		if len(numberToParse) == 0 ||
  			!PLUS_CHARS_PATTERN.MatchString(numberToParse) {
  			return false
  		}
  	}
  	return true
  }
docs: // Checks to see that the region code used is valid, or if it is not valid,
  // that the number to parse starts with a + symbol so that we can attempt
  // to infer the region from the number. Returns false if it cannot use the
  // region provided and the region cannot be inferred.