Fix typing

xarray/core/groupby.py

@@ -288,7 +288,7 @@ def _apply_loffset(
 
 
 class Grouper:
-    def __init__(self, group):
+    def __init__(self, group: T_Group):
         self.group = group
         self.codes = None
         self.labels = None
@@ -298,21 +298,21 @@ def __init__(self, group):
         self._group_as_index = None
 
     @property
-    def name(self):
+    def name(self) -> Hashable:
         return self.group1d.name
 
     @property
-    def size(self):
+    def size(self) -> int:
         return len(self)
 
-    def __len__(self):
+    def __len__(self) -> int:
         return len(self.full_index)
 
     @property
     def dims(self):
         return self.group1d.dims
 
-    def factorize(self, squeeze):
+    def factorize(self, squeeze: bool) -> None:
         raise NotImplementedError
 
     @property
@@ -328,7 +328,7 @@ def group_as_index(self) -> pd.Index:
             self._group_as_index = safe_cast_to_index(self.group1d)
         return self._group_as_index
 
-    def _resolve_group(self, obj):
+    def _resolve_group(self, obj) -> None:
         from xarray.core.dataarray import DataArray
 
         group = self.group
@@ -369,14 +369,14 @@ def _resolve_group(self, obj):
 
 
 class UniqueGrouper(Grouper):
-    def factorize(self, squeeze):
+    def factorize(self, squeeze) -> None:
         is_dimension = self.group.dims == (self.group.name,)
         if is_dimension and self.is_unique_and_monotonic:
             self._factorize_dummy(squeeze)
         else:
             self._factorize_unique()
 
-    def _factorize_unique(self):
+    def _factorize_unique(self) -> None:
         # look through group to find the unique values
         sort = not isinstance(self.group_as_index, pd.MultiIndex)
         unique_values, group_indices, codes = unique_value_groups(
@@ -393,7 +393,7 @@ def _factorize_unique(self):
         self.group_indices = group_indices
         self.full_index = self.unique_coord
 
-    def _factorize_dummy(self, squeeze):
+    def _factorize_dummy(self, squeeze) -> None:
         size = self.group.size
         # no need to factorize
         if not squeeze:
@@ -423,7 +423,7 @@ def __init__(self, group, bins, cut_kwargs):
         self.bins = bins
         self.cut_kwargs = cut_kwargs
 
-    def factorize(self, squeeze):
+    def factorize(self, squeeze: bool) -> None:
         from xarray.core.dataarray import DataArray
 
         data = self.group1d.values
@@ -526,13 +526,7 @@ def first_items(self):
                 _apply_loffset(self.loffset, first_items)
             return first_items, codes
 
-    def factorize(
-        self, squeeze
-    ) -> tuple[
-        DataArray | IndexVariable | _DummyGroup,
-        list[slice] | list[list[int]] | np.ndarray,
-        np.ndarray,
-    ]:
+    def factorize(self, squeeze: bool) -> None:
         self.full_index, first_items, codes = self._get_index_and_items()
         sbins = first_items.values.astype(np.int64)
         self.group_indices = [slice(i, j) for i, j in zip(sbins[:-1], sbins[1:])] + [