diff --git a/mapytex/stat/weightedDataset.py b/mapytex/stat/weightedDataset.py
index 4c45fa3..ca1f75c 100644
--- a/mapytex/stat/weightedDataset.py
+++ b/mapytex/stat/weightedDataset.py
@@ -1,18 +1,19 @@
 #/usr/bin/env python
 # -*- coding:Utf-8 -*-
 
-#
-#
-# Ensemble de fonction rendant beaucoup plus pratique la résolution et l'élaboration des exercices de stat au lycée
-#
-#
+"""
+ Statistical tools which should ease statistical exercises creation
+"""
+
 
 from math import sqrt, ceil
 from collections import Counter
 from .dataset import Dataset
-from ..calculus.generic import flatten_list
+from itertools import chain
 from .number_tools import number_factory
 
+def flatten_list(l):
+    return list(chain(*l))
 
 class WeightedDataset(dict):
     """ A weighted dataset with statistics and latex rendering methods