Why do the methods return an array containing the results?

[SametSahin10]

I'm trying to use ImageAnnotatorClient to annotate images. I've realized that the methods that are called on the ImageAnnotatorClient instance return Promise<[protoTypes.google.cloud.vision.v1.IAnnotateImageResponse]>. And in the examples the result is assigned and used like below:

const [result] = await client.labelDetection('./resources/wakeupcat.jpg');
const labels = result.labelAnnotations;

What is the reason of this? Why do methods not return Promise<[protoTypes.google.cloud.vision.v1.IAnnotateImageResponse]> directly?