def sense=(sense)
      @sense = sense
      sense = sense == :min ? Gurobi::GRB_MINIMIZE : Gurobi::GRB_MAXIMIZE
      ret = Gurobi.GRBsetintattr @ptr, Gurobi::GRB_INT_ATTR_MODELSENSE, sense
      fail if ret != 0
    end
def sense=(sense)
      @sense = sense
      sense = sense == :min ? Gurobi::GRB_MINIMIZE : Gurobi::GRB_MAXIMIZE
      ret = Gurobi.GRBsetintattr @ptr, Gurobi::GRB_INT_ATTR_MODELSENSE, sense
      fail if ret != 0
    end
Set the sense of the model