TYP: Fix core/groupby/generic.py lexsort attr-defined type ignore

GH37715

Author: Mateusz

pandas/core/groupby/generic.py

@@ -11,6 +11,7 @@
 from functools import partial
 from textwrap import dedent
 from typing import (
+    TYPE_CHECKING,
     Any,
     Callable,
     Hashable,
@@ -89,6 +90,9 @@
 
 from pandas.plotting import boxplot_frame_groupby
 
+if TYPE_CHECKING:
+    from pandas import Interval
+
 # TODO(typing) the return value on this callable should be any *scalar*.
 AggScalar = Union[str, Callable[..., Any]]
 # TODO: validate types on ScalarResult and move to _typing
@@ -650,12 +654,9 @@ def value_counts(
 
         if is_interval_dtype(lab.dtype):
             # TODO: should we do this inside II?
+            lab_interval = cast(Interval, lab)
 
-            # error: "ndarray" has no attribute "left"
-            # error: "ndarray" has no attribute "right"
-            sorter = np.lexsort(
-                (lab.left, lab.right, ids)  # type: ignore[attr-defined]
-            )
+            sorter = np.lexsort((lab_interval.left, lab_interval.right, ids))
         else:
             sorter = np.lexsort((lab, ids))