diff --git a/bijoe/visualization/utils.py b/bijoe/visualization/utils.py
index fb590a8..56382d8 100644
--- a/bijoe/visualization/utils.py
+++ b/bijoe/visualization/utils.py
@@ -19,7 +19,6 @@ import json
 import hashlib
 import datetime
 import decimal
-from collections import OrderedDict
 import copy
 
 from django.utils.safestring import mark_safe
@@ -29,7 +28,7 @@ from django.core.cache import cache
 from django.http import Http404
 from django.conf import settings
 
-from ..utils import get_warehouses, human_join
+from ..utils import get_warehouses
 from ..engine import Engine
 from .ods import Workbook
 
@@ -45,6 +44,7 @@ class Visualization(object):
         self.drilldown_y = drilldown_y
         self.filters = filters or {}
         self.loop = loop
+        self.members = {}
 
     @property
     def drilldown(self):