I am trying to run solver_manager_create method as it shown in the quick start code in optapy repo (https://github.com/optapy/optapy-quickstarts/blob/04fd102ee31919cacc4145d0517fe07b2627ca02/employee-scheduling/services.py#L168) But i am receiving a java.lang.IllegalArgumentException error. Full Error: what am i missing? Answer From the error message, it appears the constraint stream use one version of Shift, and the domain model use a DIFFERENT version of Shift. Do not redefine