add code sample for pandas-dev#36915

Author: simonjayhawkins

bisect/36915.py

@@ -0,0 +1,20 @@
+# BUG: Intersection of multiindex returns duplicates #36915
+
+import pandas as pd
+
+print(pd.__version__)
+
+arraysA = [["val1", "val1", "val1", "val1"], ["val2", "val2", "val2", "val2"]]
+arraysB = [["val1"], ["val2"]]
+
+indexA = pd.MultiIndex.from_arrays(arraysA, names=("idx1", "idx2"))
+indexB = pd.MultiIndex.from_arrays(arraysB, names=("idx1", "idx2"))
+
+res = indexA.intersection(indexB)
+print(res)
+
+expected = pd.MultiIndex.from_tuples([("val1", "val2")], names=["idx1", "idx2"])
+
+from pandas import testing as tm
+
+tm.assert_index_equal(res, expected)