costate from NLP solver

[SiyangMeng]

in CasADi from solver nlpsol, I could get adjoint variable lam_x if my nolinear programming variables are x' and lagrangian lam_g if the nonlinear constraints are g(x). But I can't find whether there is costate variable if I get optimal control solution, in ocl.Problem there are only children struct states, integrator, controls, parameters, h. so I ask if there is an approach to get costate variable calculated by CasADi?