Updates to correct errors revealed by mypy

Author: gwrome

pandas/core/dtypes/base.py

@@ -1,5 +1,5 @@
 """Extend pandas with custom array types"""
-from typing import List, Optional
+from typing import List, Optional, Type
 
 import numpy as np
 
@@ -209,7 +209,7 @@ def __str__(self):
         return self.name
 
     @property
-    def type(self) -> type:
+    def type(self) -> Type:
         """
         The scalar type for the array, e.g. ``int``
 

pandas/core/frame.py

@@ -19,7 +19,7 @@
 import sys
 import warnings
 from textwrap import dedent
-from typing import List, Optional, Union
+from typing import List, Optional, Set, Union
 
 import numpy as np
 import numpy.ma as ma
@@ -367,7 +367,7 @@ def _constructor(self):
     _constructor_sliced = Series
     _deprecations = NDFrame._deprecations | frozenset(
         ['get_value', 'set_value', 'from_csv', 'from_items'])
-    _accessors = set()
+    _accessors = set()  # type: Set
 
     @property
     def _constructor_expanddim(self):

pandas/core/groupby/groupby.py

@@ -12,7 +12,7 @@ class providing the base-class of operations.
 import datetime
 from functools import partial, wraps
 import types
-from typing import Optional, Tuple, Type
+from typing import Optional, Tuple, Type, Union
 import warnings
 
 import numpy as np
@@ -1736,8 +1736,9 @@ def quantile(self, q=0.5, interpolation='linear'):
         b    3.0
         """
 
-        def pre_processor(vals: np.ndarray) -> \
-                Tuple[np.ndarray, Optional[Type]]:
+        def pre_processor(
+                vals: np.ndarray
+        ) -> Tuple[np.ndarray, Optional[Union[str, Type]]]:
             if is_object_dtype(vals):
                 raise TypeError("'quantile' cannot be performed against "
                                 "'object' dtypes!")