NPM Package returning empty JSON

I’m testing your npm package with NodeJS to integrate Paybook Sync services into the company’s ReST API. I’ve been running with some problems with the response of the endpoints. It is indeed connecting to the Sync API and logging to the console the changes but it is returning an empty JSON from the backend petitions; I, therefore, can’t send the information to my frontend.

In the package documentation, to get the users, for example, the SDK Method is getUsers(options, callback) but I can’t find where are the options or parameters I can pass to this method.

¿Where can I find the options available for each endpoint and why is it not returning the information in a JSON?

In order to implement Sync API, I recommend using your favorite HTTP client.
The NPM Package is not up to date.
API Doc :
Node Examples (with request package) :