mats-knmi

This is the draft pull request that will collect all the changes that need to be made to fully integrate xarray into pysteps. Progress of this project is tracked [here](https://github.com/orgs/pySTEPS/projects/4?pane=info)....

In essence an exporter should no longer be necessary as a simple `dataset.to_netcdf(...)` call should suffice. Possibly we can rewrite the exporter to do just that.

We can add this decorator to the methods that take a dataset as one of it's arguments.

Since xarray does not natively support incremental writes (https://stackoverflow.com/questions/66231575/xarray-appending-or-rewriting-a-existing-nc-file), we need to find a solution for the callback method. - One option could be to create the initial dataset using...

The [old v2 pull request](https://github.com/pySTEPS/pysteps/pull/383), had already done this, so you can look there for how to do this.

During a recent performance improvement, there was some uncertainty on how to deal with computing the zerovalue for `precip_models_cascade`: https://github.com/pySTEPS/pysteps/pull/435#discussion_r1786151740. There is some code there that is supposed to get...

fix the remaining issues with the tests

2

I removed the importer decorator as that only caused confusion most of the time, while it didn't really add anything. Also some tests failed again because of changes I made...