Why does getMyFeesEstimate return an object?

[pwrnrd]

I'm working on a PR where we mock tests which use MWS-Simple (so pretty much all test in test-api.js) . I fixed some minor bugs which I'll include in the coming PR.

When working on mocked tests for getMyFeesEstimate, I was wondering why getMyFeesEstimate returns an object instead of an array? Is it OK if I return an array here? MWS Advanced returns arrays everywhere else (for as far is know), so this change would make the API's more consistent. In addition, the MWS API docs also state that the return value is a list (see: https://docs.developer.amazonservices.com/en_UK/products/Products_GetMyFeesEstimate.html).