feat(test): Add test hierarchy

test/data/test_hierarchy.owl

+@prefix : <http://loutre.fr/>.
+@prefix owl: <http://www.w3.org/2002/07/owl#>.
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
+
+:FirstClass a owl:Class.
+
+:SubClass a owl:Class;
+    rdfs:subClassOf :FirstClass.

test/data/test_hierarchy.yams

+from yams.buildobjs import *
+
+class FirstClass(EntityType):
+    pass
+
+class SubClass(FirstClass):
+    pass
+

test/test_owl2yams.py

@@ -34,6 +34,9 @@
     def test_transform_relation(self):
         self._load_owl_and_yams("test_relation.owl", "test_relation.yams")
 
+    def test_transform_hierarchy(self):
+        self._load_owl_and_yams("test_hierarchy.owl", "test_hierarchy.yams")
+
 
 if __name__ == "__main__":
     unittest.main()