pandas-dev#49452 Removed implentation and raised NotImplementedError.

Author: TaylorChaseHunter

pandas/core/indexes/multi.py

@@ -1465,24 +1465,9 @@ def _get_grouper_for_level(
         *,
         level=None,
         dropna: bool = True,
-    ) -> tuple[Index, npt.NDArray[np.signedinteger] | None, Index | None]:
-        if mapper is not None:
-            indexer = self.codes[level]
-            # Handle group mapping function and return
-            level_values = self.levels[level].take(indexer)
-            grouper = level_values.map(mapper)
-            return grouper, None, None
-
-        values = self.get_level_values(level)
-        codes, uniques = algos.factorize(values, sort=True, use_na_sentinel=dropna)
-        assert isinstance(uniques, Index)
-
-        if self.levels[level]._can_hold_na:
-            grouper = uniques.take(codes, fill_value=True)
-        else:
-            grouper = uniques.take(codes)
-
-        return grouper, codes, uniques
+    ):
+        raise NotImplementedError("No longer has any use.")
+        
 
     @cache_readonly
     def inferred_type(self) -> str: