private String getSignerRegion() {
        String region = getSignerRegionOverride();
        if (region == null) {
            region = clientRegion;
        }
        return region;
    }
private String getSignerRegion ( ) { String region = getSignerRegionOverride ( ) ; if ( region == null ) { region = clientRegion ; } return region ; }
Return the region string that should be used for signing requests sent by
this client. This method can only return null if both of the following
are true:
(a) the user has never specified a region via setRegion/configureRegion/setSignerRegionOverride
(b) the user has specified a client endpoint that is known to be a global S3 endpoint