From dd03c196d684d6ed594ee58451b0a36d7935a1ea Mon Sep 17 00:00:00 2001
From: Simon Hawkins <simonjayhawkins@gmail.com>
Date: Wed, 12 Feb 2020 15:58:56 +0000
Subject: [PATCH] TYP: pandas/core/dtypes/base.py (#31352)

---
 pandas/core/dtypes/base.py | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/pandas/core/dtypes/base.py b/pandas/core/dtypes/base.py
index 618a35886a905..a4f0ccc2016c0 100644
--- a/pandas/core/dtypes/base.py
+++ b/pandas/core/dtypes/base.py
@@ -2,7 +2,7 @@
 Extend pandas with custom array types.
 """
 
-from typing import Any, List, Optional, Tuple, Type
+from typing import TYPE_CHECKING, Any, List, Optional, Tuple, Type
 
 import numpy as np
 
@@ -10,6 +10,9 @@
 
 from pandas.core.dtypes.generic import ABCDataFrame, ABCIndexClass, ABCSeries
 
+if TYPE_CHECKING:
+    from pandas.core.arrays import ExtensionArray  # noqa: F401
+
 
 class ExtensionDtype:
     """
@@ -29,7 +32,6 @@ class ExtensionDtype:
 
     * type
     * name
-    * construct_from_string
 
     The following attributes influence the behavior of the dtype in
     pandas operations
@@ -74,7 +76,7 @@ class property**.
         class ExtensionDtype:
 
             def __from_arrow__(
-                self, array: pyarrow.Array/ChunkedArray
+                self, array: Union[pyarrow.Array, pyarrow.ChunkedArray]
             ) -> ExtensionArray:
                 ...
 
@@ -122,11 +124,11 @@ def __eq__(self, other: Any) -> bool:
     def __hash__(self) -> int:
         return hash(tuple(getattr(self, attr) for attr in self._metadata))
 
-    def __ne__(self, other) -> bool:
+    def __ne__(self, other: Any) -> bool:
         return not self.__eq__(other)
 
     @property
-    def na_value(self):
+    def na_value(self) -> object:
         """
         Default NA value to use for this type.
 
@@ -184,7 +186,7 @@ def names(self) -> Optional[List[str]]:
         return None
 
     @classmethod
-    def construct_array_type(cls):
+    def construct_array_type(cls) -> Type["ExtensionArray"]:
         """
         Return the array type associated with this dtype.
 
@@ -250,7 +252,7 @@ def construct_from_string(cls, string: str):
         return cls()
 
     @classmethod
-    def is_dtype(cls, dtype) -> bool:
+    def is_dtype(cls, dtype: object) -> bool:
         """
         Check if we match 'dtype'.
 
@@ -261,7 +263,7 @@ def is_dtype(cls, dtype) -> bool:
 
         Returns
         -------
-        is_dtype : bool
+        bool
 
         Notes
         -----