Add MultiIndex.rename API(#7172)

Closes #7057 

Properly overrides `MultiIndex.rename` from `Index.rename`, reusing API from `MultiIndex.set_names`.

Authors:
  - Michael Wang <isVoid@users.noreply.github.com>

Approvers:
  - GALI PREM SAGAR (@galipremsagar)

URL: #7172

python/cudf/cudf/core/multiindex.py

@@ -185,6 +185,53 @@ def names(self, value):
         assert len(value) == self.nlevels
         self._names = pd.core.indexes.frozen.FrozenList(value)
 
+    def rename(self, names, inplace=False):
+        """
+        Alter MultiIndex level names
+
+        Parameters
+        ----------
+        names : list of label
+            Names to set, length must be the same as number of levels
+        inplace : bool, default False
+            If True, modifies objects directly, otherwise returns a new
+            ``MultiIndex`` instance
+
+        Returns
+        --------
+        None or MultiIndex
+
+        Examples
+        --------
+        Renaming each levels of a MultiIndex to specified name:
+
+        >>> midx = cudf.MultiIndex.from_product(
+                [('A', 'B'), (2020, 2021)], names=['c1', 'c2'])
+        >>> midx.rename(['lv1', 'lv2'])
+        MultiIndex([('A', 2020),
+                    ('A', 2021),
+                    ('B', 2020),
+                    ('B', 2021)],
+                names=['lv1', 'lv2'])
+        >>> midx.rename(['lv1', 'lv2'], inplace=True)
+        >>> midx
+        MultiIndex([('A', 2020),
+                    ('A', 2021),
+                    ('B', 2020),
+                    ('B', 2021)],
+                names=['lv1', 'lv2'])
+
+        ``names`` argument must be a list, and must have same length as
+        ``MultiIndex.levels``:
+
+        >>> midx.rename(['lv0'])
+        Traceback (most recent call last):
+        ValueError: Length of names must match number of levels in MultiIndex.
+
+        """
+
+        return self.set_names(names, level=None, inplace=inplace)
+
     def set_names(self, names, level=None, inplace=False):
         if (
             level is not None

python/cudf/cudf/tests/test_multiindex.py

@@ -1452,3 +1452,52 @@ def test_multiindex_set_names_error(level, names):
         lfunc_args_and_kwargs=([], {"names": names, "level": level}),
         rfunc_args_and_kwargs=([], {"names": names, "level": level}),
     )
+
+
+@pytest.mark.parametrize(
+    "idx",
+    [
+        pd.MultiIndex.from_product([["python", "cobra"], [2018, 2019]]),
+        pd.MultiIndex.from_product(
+            [["python", "cobra"], [2018, 2019]], names=["old name", None]
+        ),
+    ],
+)
+@pytest.mark.parametrize(
+    "names",
+    [
+        [None, None],
+        ["a", None],
+        ["new name", "another name"],
+        [1, None],
+        [2, 3],
+        [42, "name"],
+    ],
+)
+@pytest.mark.parametrize("inplace", [True, False])
+def test_multiindex_rename(idx, names, inplace):
+    pi = idx.copy()
+    gi = cudf.from_pandas(idx)
+
+    expected = pi.rename(names=names, inplace=inplace)
+    actual = gi.rename(names=names, inplace=inplace)
+
+    if inplace:
+        expected, actual = pi, gi
+
+    assert_eq(expected, actual)
+
+
+@pytest.mark.parametrize(
+    "names", ["plain string", 123, ["str"], ["l1", "l2", "l3"]]
+)
+def test_multiindex_rename_error(names):
+    pi = pd.MultiIndex.from_product([["python", "cobra"], [2018, 2019]])
+    gi = cudf.from_pandas(pi)
+
+    assert_exceptions_equal(
+        lfunc=pi.rename,
+        rfunc=gi.rename,
+        lfunc_args_and_kwargs=([], {"names": names}),
+        rfunc_args_and_kwargs=([], {"names": names}),
+    )