Check for all __init__ parameters being saved to idata.attrs

[wd60622]

The idata.attrs is used to reconstruct the model with save and load methods. This is a bit hard to keep the __init__, _save_input_params and load methods in sync.

Some check and test for this would be nice addition.

Potentially, the set_idata_attrs can be create_idata_attrs such that the model doesn't have to be fit in order to know if the model will not be able to saved properly.
Then the workflow in fit can be:

• create_idata_attrs (fast and raise)
• pm.sample (long)
• set_idata_attrs