respell symetric

schema.py

@@ -50,7 +50,7 @@
     content  = String(fulltextindexed=True)
     content_format = String(required=True, meta=True, maxsize=50)
     ordernum = Int(required=True)
-    alternative = SubjectRelation('EmailPart', symetric=True)
+    alternative = SubjectRelation('EmailPart', symmetric=True)
 
 
 class EmailThread(EntityType):