This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
public interface StageResolver<T>
Resolves Amazon API Gateway Stage from input event.
An Amazon ApiGateway stage is a logical reference to a lifecycle state of your API (for example, dev, prod, beta, or v2). API stages are identified by their API ID and stage name, and they're included in the URL you use to invoke the API.