How to add a multi-dimensional state variable

Just like normal JuMP variables, it is possible to create containers of state variables.

julia> model = SDDP.LinearPolicyGraph(           stages=1, lower_bound = 0, optimizer = HiGHS.Optimizer       ) do subproblem, t           # A scalar state variable.           @variable(subproblem, x >= 0, SDDP.State, initial_value = 0)           println("Lower bound of outgoing x is: ", lower_bound(x.out))           # A vector of state variables.           @variable(subproblem, y[i = 1:2] >= i, SDDP.State, initial_value = i)           println("Lower bound of outgoing y[1] is: ", lower_bound(y[1].out))           # A JuMP.Containers.DenseAxisArray of state variables.           @variable(subproblem,               z[i = 3:4, j = [:A, :B]] >= i, SDDP.State, initial_value = i)           println("Lower bound of outgoing z[3, :B] is: ", lower_bound(z[3, :B].out))       end;Lower bound of outgoing x is: 0.0Lower bound of outgoing y[1] is: 1.0Lower bound of outgoing z[3, :B] is: 3.0