Incorrect  Bucket File download Api

I've looked into the code Firebase Bucket Storage File (firebase-admin: "8.3.0") and found that when we call download - the content should be returned in any case..
```
  export declare type DownloadResponse = [Buffer];
  export declare type DownloadCallback = (err: RequestError | null, contents: Buffer) => void;
```
What do you think about this?
Thanks.