Attributes should define is_set_by_optimize

[odow]

See the discussions here: https://github.com/jump-dev/JuMP.jl/issues/2587 https://github.com/jump-dev/JuMP.jl/pull/2784

[metab0t]

Does https://github.com/jump-dev/JuMP.jl/issues/2587#issuecomment-834065020 solve the problem? Based on fix of JuMP side above, should we define the following code here to solve this problem?

MOI.is_set_by_optimize(::ModelAttribute) = true
MOI.is_set_by_optimize(::VariableAttribute) = true
MOI.is_set_by_optimize(::ConstraintAttribute) = true

[odow]

Yes, I think that's sufficient for now.