Add missing classmethod decorator

diff --git a/pypol/domains.py b/pypol/domains.py
index 6b47fe8..b4780fc 100644 (file)
--- a/pypol/domains.py
+++ b/pypol/domains.py
@@ -249,6 +249,7 @@ class Domain:
             self._dimension = len(self._symbols)
             return self
 
+    @classmethod
     def _toislset(cls, polyhedra, symbols):
         polyhedron = polyhedra[0]
         islbset = polyhedron._toislbasicset(polyhedron.equalities,