public boolean isPlaneDefined(ToShapeId service) {
        return servicePlanes.containsKey(service.toShapeId());
    }
Checks if the given service shape has defined its plane.

@param service Service to check.
@return Returns true if the service has defined its plane.
smithy-aws-traits/src/main/java/software/amazon/smithy/aws/traits/PlaneIndex.java