AWS S3 region identifier, passing in custom values is also possible, in that case it is up to you to pass a valid endpoint, otherwise boom will happen :)
Example
use FromStr;
use Region;
// Parse from a string
let region: Region = "us-east-1".parse.unwrap;
// Choose region directly
let region = EuWest2;
// Custom region requires valid region name and endpoint
let region_name = "nl-ams".to_string;
let endpoint = "https://s3.nl-ams.scw.cloud".to_string;
let region = Custom ;