fix(multi heritage): Handle multi heritage using string join

This needs open-source/logilab-common!46
before publish

owl2yams/__init__.py

@@ -178,13 +178,7 @@
             if superior_class_fragment is not None:
                 superior_classes.append(superior_class_fragment)
         if superior_classes:
-            if len(superior_classes) > 1:
-                print(
-                    f"Warning: multi-heritage is not support yet. {class_fragment} will specialize",
-                    f"{superior_classes[0]} and {', '.join(superior_classes[1::])}",
-                    "specialization will be ignored",
-                )
-            entity_schema._specialized_type = superior_classes[0]
+            entity_schema._specialized_type = ", ".join(superior_classes)
 
     # 2. fetch all datatype properties