- symbols = self._xsymbols([self, other])
- islset1 = self._toislset(self.polyhedra, symbols)
- islset2 = self._toislset(other.polyhedra, symbols)
- equal = bool(libisl.isl_set_is_strict_subset(islset1, islset2))
- libisl.isl_set_free(islset1)
- libisl.isl_set_free(islset2)
- return equal
+ if isinstance(other, Domain):
+ symbols = self._xsymbols([self, other])
+ islset1 = self._toislset(self.polyhedra, symbols)
+ islset2 = self._toislset(other.polyhedra, symbols)
+ equal = bool(libisl.isl_set_is_strict_subset(islset1, islset2))
+ libisl.isl_set_free(islset1)
+ libisl.isl_set_free(islset2)
+ return equal
+ return NotImplemented