Use reverse relation to determine type.

rssfieper/models.py

@@ -95,7 +95,8 @@ class SocialMedia(models.Model):
 
     @property
     def type(self):
-        return self.__class__.__name__[11:].lower()
+        if self.socialmediatwitter:
+            return 'twitter'
 
 class SocialMediaTwitter(SocialMedia):
     oauth_access_token = models.CharField(max_length=1024)