Allow MILP bipartite observations in the SOLVING stage ?

[gasse]

@dchetelat do you think this will cause any issue ? I suppose if that passes all the tests then we should be ok ?

[dchetelat]

Hmm I told you it was fine on Slack, but thinking about it again I can think of a possible issue - cuts? Are cuts considered constraints?

[gasse]

Hmmm looks like the tests do fail...

        def test_extract(observation_function, model):
    
            """Obtain observation."""
    
            observation_function.before_reset(model)
    
            pytest.helpers.advance_to_stage(model, ecole.scip.Stage.Solving)
    
    >       observation_function.extract(model, False)
    
    E       ecole.core.scip.Exception: Constraint 0 cannot be expressed as a single linear constraint (type "bounddisjunction"), MilpBipartite observation cannot be extracted.
    ```

[dchetelat]

I see - I wonder where it's coming from. Preprocessing? Branching? Cuts?