FIxed Example 3 in violin string-doc

Kully · Kully · commit 36f7e3ca19e9 · 2016-06-15T10:59:49.000-04:00
diff --git a/plotly/tools.py b/plotly/tools.py
@@ -2142,6 +2142,7 @@ def create_violin(data, data_header=None, group_header=None,
         group_header = 'Group'
 
         # make groupby object with pandas
+        group_stats = {}
         groupby_data = df.groupby([group_header])
 
         for group in "ABCDE":
