Update fit.py
Added docstring specifying that model is not extracted in `MapDataset.to_spectrum_dataset`
@@ -821,6 +821,9 @@ class MapDataset(Dataset):
EnergyDispersion is obtained at the on_region center.
Only regions with centers are supported.
+ The model is not exported to the ~gammapy.spectrum.SpectrumDataset.
+ It must be set after the dataset extraction.
+
Parameters
----------
on_region : `~regions.SkyRegion`
