code: public void put(Var var, int state) {
          if (state < 0 || state >= var.getNumStates()) {
              throw new IllegalArgumentException("Invalid state idx " + state + " for var " + var);
          }
          config.put(var, state);
          vars.add(var);
      }
docs: Sets the state value to state for the given variable, adding it if necessary.