Something I just noticed now: According to this L116 in tropo_pyaps3.py you only accept ERA5.

The PR checks all the tropo models that were in model.cfg (ERA, MERRA, ECMWF, etc). If you are not accepting other models maybe the model.cfg can be cleaned up for clarity. I can also revise the code to remove checks for unused tropo models.

Thank you @pbrotoisworo. I just cleaned up the model.cfg a little bit following your suggestion (yunjunz/PyAPS@3ba82ff).

For the checking here, either removing the other models or keeping them is good to me. If we keep all of them, it will be good to move this checking to an independent function, and call it here.

Below is for your reference:
[CDS] -> ERA5
[ECMWF] -> ERAI
[MERRA] -> MERRA
No checking is required for NARR.
All the others are irrelevant.

@yunjunz. I've created a separate function to check the pyaps config and kept the other tropo models to prevent errors if people want to use them in the future.

The function will check for default values (e.g your-uid:your-api-key) and empty values for the selected tropo model.