diff --git a/senpy/models.py b/senpy/models.py
index 7f967da..250de26 100644
--- a/senpy/models.py
+++ b/senpy/models.py
@@ -140,7 +140,7 @@ class SenpyMixin(object):
                     vp = item[kp]
                     temp[kp] = ser_or_down(vp)
                 return temp
-            elif isinstance(item, list):
+            elif isinstance(item, list) or isinstance(item, set):
                 return list(ser_or_down(i) for i in item)
             else:
                 return item
@@ -184,7 +184,7 @@ class SenpyMixin(object):
         jsonschema.validate(obj, self.schema)
 
     def __str__(self):
-        return str(self.to_JSON())
+        return str(self.serialize())
 
 
 class BaseModel(SenpyMixin, dict):
diff --git a/tests/test_plugins.py b/tests/test_plugins.py
index 0108194..c7fdeab 100644
--- a/tests/test_plugins.py
+++ b/tests/test_plugins.py
@@ -181,6 +181,7 @@ class PluginsTest(TestCase):
             "centroids_direction": ["emoml:big6", "emoml:fsre-dimensions"]
         }
         c = CentroidConversion(info)
+        print(c.serialize())
 
         es1 = EmotionSet()
         e1 = Emotion()
@@ -189,6 +190,7 @@ class PluginsTest(TestCase):
         res = c._forward_conversion(es1)
         assert res["X-dimension"] == 0.5
         assert res["Y-dimension"] == 0.5
+        print(res)
 
         e2 = Emotion()
         e2.onyx__hasEmotionCategory = "c2"
@@ -196,12 +198,14 @@ class PluginsTest(TestCase):
         res = c._forward_conversion(es1)
         assert res["X-dimension"] == 0
         assert res["Y-dimension"] == 1
+        print(res)
 
         e = Emotion()
         e["X-dimension"] = -0.2
         e["Y-dimension"] = -0.3
         res = c._backwards_conversion(e)
         assert res["onyx:hasEmotionCategory"] == "c3"
+        print(res)
 
         e = Emotion()
         e["X-dimension"] = -0.2