def METHOD_NAME(self):
    M = ConcreteModel()
    M.v = Var({1, 2, 3})
    try:
        M.c = SOSConstraint(var=M.v, sos=2)
        self.fail("Expected ValueError")
    except ValueError:
        pass
    M = ConcreteModel()
    M.s = Set(initialize=[1, 2, 3], ordered=True)
    M.v = Var(M.s)
    M.c = SOSConstraint(var=M.v, sos=2)