Add comments about change

Author: cmazzullo

pandas/tests/groupby/test_groupby.py

@@ -756,6 +756,7 @@ def test_frame_describe_multikey(self):
         desc_groups = []
         for col in self.tsframe:
             group = grouped[col].describe()
+            # GH 17464 - Remove duplicate MultiIndex levels
             group_col = pd.MultiIndex(
                 levels=[[col], group.columns],
                 labels=[[0]*len(group.columns), range(len(group.columns))])
@@ -770,6 +771,7 @@ def test_frame_describe_multikey(self):
                                          'C': 1, 'D': 1}, axis=1)
         result = groupedT.describe()
         expected = self.tsframe.describe().T
+        # GH 17464 - Remove duplicate MultiIndex levels
         expected.index = pd.MultiIndex(levels=[[0, 1], expected.index],
                                        labels=[[0, 0, 1, 1], range(len(expected.index))])
         tm.assert_frame_equal(result, expected)