diff --git a/pdfplumber/container.py b/pdfplumber/container.py
index 9a9148c..2d664fe 100644
--- a/pdfplumber/container.py
+++ b/pdfplumber/container.py
@@ -13,14 +13,17 @@ class Container(object):
     cached_properties = ["_rect_edges", "_curve_edges", "_edges", "_objects"]
 
     @property
-    def pages(self) -> Optional[List[Any]]: ...  # pragma: nocover
+    def pages(self) -> Optional[List[Any]]:  # pragma: nocover
+        raise NotImplementedError
 
     @property
-    def objects(self) -> Dict[str, T_obj_list]: ...  # pragma: nocover
+    def objects(self) -> Dict[str, T_obj_list]:  # pragma: nocover
+        raise NotImplementedError
 
     def to_dict(
         self, object_types: Optional[List[str]] = None
-    ) -> Dict[str, Any]: ...  # pragma: nocover
+    ) -> Dict[str, Any]:  # pragma: nocover
+        raise NotImplementedError
 
     def flush_cache(self, properties: Optional[List[str]] = None) -> None:
         props = self.cached_properties if properties is None else properties
diff --git a/pdfplumber/table.py b/pdfplumber/table.py
index 7fae68e..e032f68 100644
--- a/pdfplumber/table.py
+++ b/pdfplumber/table.py
@@ -501,7 +501,7 @@ class TableSettings:
     intersection_y_tolerance: T_num = UNSET
     text_settings: Optional[Dict[str, Any]] = None
 
-    def __post_init__(self) -> "TableSettings":
+    def __post_init__(self) -> None:
         """Clean up user-provided table settings.
 
         Validates that the table settings provided consists of acceptable values and
@@ -552,8 +552,6 @@ class TableSettings:
             if getattr(self, attr) is UNSET:
                 setattr(self, attr, getattr(self, fallback))
 
-        return self
-
     @classmethod
     def resolve(cls, settings: Optional[T_table_settings]) -> "TableSettings":
         if settings is None:
diff --git a/pdfplumber/utils/clustering.py b/pdfplumber/utils/clustering.py
index 961ab31..b65b4d5 100644
--- a/pdfplumber/utils/clustering.py
+++ b/pdfplumber/utils/clustering.py
@@ -1,9 +1,9 @@
 import itertools
 from collections.abc import Hashable
 from operator import itemgetter
-from typing import Callable, Dict, Iterable, List, TypeVar, Union
+from typing import Any, Callable, Dict, Iterable, List, Tuple, TypeVar, Union
 
-from .._typing import T_num
+from .._typing import T_num, T_obj
 
 
 def cluster_list(xs: List[T_num], tolerance: T_num = 0) -> List[List[T_num]]:
@@ -36,15 +36,15 @@ def make_cluster_dict(values: Iterable[T_num], tolerance: T_num) -> Dict[T_num,
     return dict(itertools.chain(*nested_tuples))
 
 
-R = TypeVar("R")
+Clusterable = TypeVar("Clusterable", T_obj, Tuple[Any, ...])
 
 
 def cluster_objects(
-    xs: List[R],
-    key_fn: Union[Hashable, Callable[[R], T_num]],
+    xs: List[Clusterable],
+    key_fn: Union[Hashable, Callable[[Clusterable], T_num]],
     tolerance: T_num,
     preserve_order: bool = False,
-) -> List[List[R]]:
+) -> List[List[Clusterable]]:
 
     if not callable(key_fn):
         key_fn = itemgetter(key_fn)
diff --git a/pdfplumber/utils/geometry.py b/pdfplumber/utils/geometry.py
index 0f84e1d..93f5f3b 100644
--- a/pdfplumber/utils/geometry.py
+++ b/pdfplumber/utils/geometry.py
@@ -30,7 +30,8 @@ def obj_to_bbox(obj: T_obj) -> T_bbox:
     """
     Return the bounding box for an object.
     """
-    return bbox_getter(obj)
+    bbox: T_bbox = bbox_getter(obj)
+    return bbox
 
 
 def bbox_to_rect(bbox: T_bbox) -> Dict[str, T_num]:
diff --git a/requirements-dev.txt b/requirements-dev.txt
index ed81d31..3e2b23b 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -2,9 +2,9 @@ black==24.8.0
 flake8==7.1.1
 isort==5.13.2
 jupyterlab==3.6.7
-mypy==0.981
+mypy==1.11.1
 nbexec==0.2.0
-pandas-stubs==2.2.2.240603
+pandas-stubs==2.2.2.240805
 pandas==2.2.2
 py==1.11.0
 pytest-cov==5.0.0