state_invariant_list : state_invariant_list state_invariant_def
                                | state_invariant_def

def p_state_invariant_list(self, p):
        '''state_invariant_list : state_invariant_list state_invariant_def
                                | state_invariant_def'''
        if len(p) == 3:
            p[1].append(p[2])
            p[0] = p[1]
        elif len(p) == 2:
            p[0] = [p[1]]