model foobarclass fooattributes  bar_attr : Integeroperations  bar_op() : Integer = bar_attr + 1constraints  inv OK1 : 0 <= self.bar_attr -- explicit self accepted  inv OK2 : 0 <= bar_attr      -- implicit self accepted  inv OK3 : 1 <= self.bar_op() -- explicit self accepted  inv notOK : 1 <= bar_op()      -- implicit self not accepted, USE error producedend