code: func GetRegionCodeForCountryCode(countryCallingCode int) string {
  	var regionCodes []string = CountryCodeToRegion[countryCallingCode]
  	if len(regionCodes) == 0 {
  		return UNKNOWN_REGION
  	}
  	return regionCodes[0]
  }
docs: // Returns the region code that matches the specific country calling code.
  // In the case of no region code being found, ZZ will be returned. In the
  // case of multiple regions, the one designated in the metadata as the
  // "main" region for this calling code will be returned. If the
  // countryCallingCode entered is valid but doesn't match a specific region
  // (such as in the case of non-geographical calling codes like 800) the
  // value "001" will be returned (corresponding to the value for World in
  // the UN M.49 schema).