[BUG] MultiIndex.values cannot generate an array of tuples

[galipremsagar]

Describe the bug
pd.MultiIndex.values generates a numpy array of tuples. However cudf.MultiIndex.values only returns a cupy array - however there is no support to store tuples in cupy arrays. Hence, at least when pandas-compatibility mode is turned on, we need to throw an error.

Steps/Code to reproduce bug

In [13]: import pandas as pd

In [15]: import numpy as np

In [16]: i = pd.MultiIndex.from_product(
    ...:         [np.arange(9, -1, -1), np.arange(9, -1, -1)], names=["one", "two"]
    ...:     )

In [17]: midx = cudf.from_pandas(i)

In [18]: midx
Out[18]: 
MultiIndex([(9, 9),
            (9, 8),
            (9, 7),
            (9, 6),
            (9, 5),
            (9, 4),
            (9, 3),
            (9, 2),
            (9, 1),
            (9, 0),
            (8, 9),
            (8, 8),
            (8, 7),
            (8, 6),
            (8, 5),
            (8, 4),
            (8, 3),
            (8, 2),
            (8, 1),
            (8, 0),
            (7, 9),
            (7, 8),
            (7, 7),
            (7, 6),
            (7, 5),
            (7, 4),
            (7, 3),
            (7, 2),
            (7, 1),
            (7, 0),
            (6, 9),
            (6, 8),
            (6, 7),
            (6, 6),
            (6, 5),
            (6, 4),
            (6, 3),
            (6, 2),
            (6, 1),
            (6, 0),
            (5, 9),
            (5, 8),
            (5, 7),
            (5, 6),
            (5, 5),
            (5, 4),
            (5, 3),
            (5, 2),
            (5, 1),
            (5, 0),
            (4, 9),
            (4, 8),
            (4, 7),
            (4, 6),
            (4, 5),
            (4, 4),
            (4, 3),
            (4, 2),
            (4, 1),
            (4, 0),
            (3, 9),
            (3, 8),
            (3, 7),
            (3, 6),
            (3, 5),
            (3, 4),
            (3, 3),
            (3, 2),
            (3, 1),
            (3, 0),
            (2, 9),
            (2, 8),
            (2, 7),
            (2, 6),
            (2, 5),
            (2, 4),
            (2, 3),
            (2, 2),
            (2, 1),
            (2, 0),
            (1, 9),
            (1, 8),
            (1, 7),
            (1, 6),
            (1, 5),
            (1, 4),
            (1, 3),
            (1, 2),
            (1, 1),
            (1, 0),
            (0, 9),
            (0, 8),
            (0, 7),
            (0, 6),
            (0, 5),
            (0, 4),
            (0, 3),
            (0, 2),
            (0, 1),
            (0, 0)],
           names=['one', 'two'])

In [19]: i
Out[19]: 
MultiIndex([(9, 9),
            (9, 8),
            (9, 7),
            (9, 6),
            (9, 5),
            (9, 4),
            (9, 3),
            (9, 2),
            (9, 1),
            (9, 0),
            (8, 9),
            (8, 8),
            (8, 7),
            (8, 6),
            (8, 5),
            (8, 4),
            (8, 3),
            (8, 2),
            (8, 1),
            (8, 0),
            (7, 9),
            (7, 8),
            (7, 7),
            (7, 6),
            (7, 5),
            (7, 4),
            (7, 3),
            (7, 2),
            (7, 1),
            (7, 0),
            (6, 9),
            (6, 8),
            (6, 7),
            (6, 6),
            (6, 5),
            (6, 4),
            (6, 3),
            (6, 2),
            (6, 1),
            (6, 0),
            (5, 9),
            (5, 8),
            (5, 7),
            (5, 6),
            (5, 5),
            (5, 4),
            (5, 3),
            (5, 2),
            (5, 1),
            (5, 0),
            (4, 9),
            (4, 8),
            (4, 7),
            (4, 6),
            (4, 5),
            (4, 4),
            (4, 3),
            (4, 2),
            (4, 1),
            (4, 0),
            (3, 9),
            (3, 8),
            (3, 7),
            (3, 6),
            (3, 5),
            (3, 4),
            (3, 3),
            (3, 2),
            (3, 1),
            (3, 0),
            (2, 9),
            (2, 8),
            (2, 7),
            (2, 6),
            (2, 5),
            (2, 4),
            (2, 3),
            (2, 2),
            (2, 1),
            (2, 0),
            (1, 9),
            (1, 8),
            (1, 7),
            (1, 6),
            (1, 5),
            (1, 4),
            (1, 3),
            (1, 2),
            (1, 1),
            (1, 0),
            (0, 9),
            (0, 8),
            (0, 7),
            (0, 6),
            (0, 5),
            (0, 4),
            (0, 3),
            (0, 2),
            (0, 1),
            (0, 0)],
           names=['one', 'two'])

In [20]: i.values
Out[20]: 
array([(9, 9), (9, 8), (9, 7), (9, 6), (9, 5), (9, 4), (9, 3), (9, 2),
       (9, 1), (9, 0), (8, 9), (8, 8), (8, 7), (8, 6), (8, 5), (8, 4),
       (8, 3), (8, 2), (8, 1), (8, 0), (7, 9), (7, 8), (7, 7), (7, 6),
       (7, 5), (7, 4), (7, 3), (7, 2), (7, 1), (7, 0), (6, 9), (6, 8),
       (6, 7), (6, 6), (6, 5), (6, 4), (6, 3), (6, 2), (6, 1), (6, 0),
       (5, 9), (5, 8), (5, 7), (5, 6), (5, 5), (5, 4), (5, 3), (5, 2),
       (5, 1), (5, 0), (4, 9), (4, 8), (4, 7), (4, 6), (4, 5), (4, 4),
       (4, 3), (4, 2), (4, 1), (4, 0), (3, 9), (3, 8), (3, 7), (3, 6),
       (3, 5), (3, 4), (3, 3), (3, 2), (3, 1), (3, 0), (2, 9), (2, 8),
       (2, 7), (2, 6), (2, 5), (2, 4), (2, 3), (2, 2), (2, 1), (2, 0),
       (1, 9), (1, 8), (1, 7), (1, 6), (1, 5), (1, 4), (1, 3), (1, 2),
       (1, 1), (1, 0), (0, 9), (0, 8), (0, 7), (0, 6), (0, 5), (0, 4),
       (0, 3), (0, 2), (0, 1), (0, 0)], dtype=object)

In [21]: midx.values
Out[21]: 
array([[9, 9],
       [9, 8],
       [9, 7],
       [9, 6],
       [9, 5],
       [9, 4],
       [9, 3],
       [9, 2],
       [9, 1],
       [9, 0],
       [8, 9],
       [8, 8],
       [8, 7],
       [8, 6],
       [8, 5],
       [8, 4],
       [8, 3],
       [8, 2],
       [8, 1],
       [8, 0],
       [7, 9],
       [7, 8],
       [7, 7],
       [7, 6],
       [7, 5],
       [7, 4],
       [7, 3],
       [7, 2],
       [7, 1],
       [7, 0],
       [6, 9],
       [6, 8],
       [6, 7],
       [6, 6],
       [6, 5],
       [6, 4],
       [6, 3],
       [6, 2],
       [6, 1],
       [6, 0],
       [5, 9],
       [5, 8],
       [5, 7],
       [5, 6],
       [5, 5],
       [5, 4],
       [5, 3],
       [5, 2],
       [5, 1],
       [5, 0],
       [4, 9],
       [4, 8],
       [4, 7],
       [4, 6],
       [4, 5],
       [4, 4],
       [4, 3],
       [4, 2],
       [4, 1],
       [4, 0],
       [3, 9],
       [3, 8],
       [3, 7],
       [3, 6],
       [3, 5],
       [3, 4],
       [3, 3],
       [3, 2],
       [3, 1],
       [3, 0],
       [2, 9],
       [2, 8],
       [2, 7],
       [2, 6],
       [2, 5],
       [2, 4],
       [2, 3],
       [2, 2],
       [2, 1],
       [2, 0],
       [1, 9],
       [1, 8],
       [1, 7],
       [1, 6],
       [1, 5],
       [1, 4],
       [1, 3],
       [1, 2],
       [1, 1],
       [1, 0],
       [0, 9],
       [0, 8],
       [0, 7],
       [0, 6],
       [0, 5],
       [0, 4],
       [0, 3],
       [0, 2],
       [0, 1],
       [0, 0]])

Expected behavior
Raise an error.

Environment overview (please complete the following information)

• Environment location: [Bare-metal]
• Method of cuDF install: [from source]