I notice an issue that if there is a linear expression that only contains constants, some of the methods seem a bit strange.
For example if I do expr.to_polars() I get a pl.DataFrame with 0 rows

I notice an issue that if there is a linear expression that only contains constants, some of the methods seem a bit strange. For example if I do expr.to_polars() I get a pl.DataFrame with 0 rows

ah right, I haven't thought about that. I guess we would need to fix that one in particular. would you be able to do so? (could also be a follow up)

@FabianHofmann I made some fixes to the "to_polars" thing for Linear and Quadratic expressions that are constant
I can't merge because of some weird PyPSA-Eur test

@FabianHofmann ready to merge if you are happy with it

@RobbieKiwi I took the freedom to push some fixes. would merge when the ci is through