Helper available to the query APIs that have region support.

query.setRegion(region)

• 'region' - parameter that must be one of the following: us-east-1, us-west-1, us-west-2, eu-west-1, ap-southeast-1, ap-northeast-1.

This translates as:

'us-east-1' =>  Virginia
'us-west-1' => N. California
'us-west-2' => Oregon
'eu-west-1' => Ireland
'ap-southeast-1' => Singapore
'ap-northeast-1' => Tokyo

Failing to use a proper region argument throws an Error.

Makes it easier to set the region to operate instead of manually passing the API endpoint to the query.request() method, or implementing setEndPoint() for the query APIs. The endpoint value may be returned by client.getEndPoint().

This method is chainable (aka it returns the client object).