TST: updated test to raise an error because of an incomplete function

unittests/test_high_level_api.py

@@ -258,5 +258,5 @@ def test_conversion_to_entity():
     rconv = convert_to_entity(obj)
     assert (rconv.get_property("ref").value.get_property("a").value
             == r.get_property("ref").value.get_property("a").value)
-    assert len(rconv.properties) == len(r.properties)
-    assert len(rconv.parents) == len(r.parents)
+    # TODO: improve compare_entities function
+    raise NotImplementedError()