+    def like(self, user):
+        from social.utils import likes, get_set, set_sets
+        if not likes(user, self):
+            tag = get_set(user, '')
+            set_sets(user, self, [tag])
+
+    def unlike(self, user):
+        from social.utils import likes, set_sets
+        if likes(user, self):
+            set_sets(user, self, [])
+
+    def full_sort_key(self):
+        return self.SORT_KEY_SEP.join((self.sort_key_author, self.sort_key, str(self.id)))
+
+    def cover_color(self):
+        return WLCover.epoch_colors.get(self.extra_info.get('epoch'), '#000000')
+