Fix Type Annotation in pandas.core.accessor (#26147)

Author: vaibhavhrt

mypy.ini

@@ -11,15 +11,9 @@ ignore_errors=True
 [mypy-pandas.compat.numpy.function]
 ignore_errors=True
 
-[mypy-pandas.core.accessor]
-ignore_errors=True
-
 [mypy-pandas.core.api]
 ignore_errors=True
 
-[mypy-pandas.core.apply]
-ignore_errors=True
-
 [mypy-pandas.core.arrays.array_]
 ignore_errors=True
 
@@ -32,15 +26,9 @@ ignore_errors=True
 [mypy-pandas.core.arrays.interval]
 ignore_errors=True
 
-[mypy-pandas.core.arrays.numpy_]
-ignore_errors=True
-
 [mypy-pandas.core.arrays.period]
 ignore_errors=True
 
-[mypy-pandas.core.arrays.sparse]
-ignore_errors=True
-
 [mypy-pandas.core.arrays.timedeltas]
 ignore_errors=True
 
@@ -98,9 +86,6 @@ ignore_errors=True
 [mypy-pandas.core.series]
 ignore_errors=True
 
-[mypy-pandas.core.sparse.frame]
-ignore_errors=True
-
 [mypy-pandas.core.util.hashing]
 ignore_errors=True
 

pandas/core/accessor.py

@@ -5,13 +5,14 @@
 that can be mixed into or pinned onto other pandas classes.
 
 """
+from typing import Set
 import warnings
 
 from pandas.util._decorators import Appender
 
 
 class DirNamesMixin:
-    _accessors = frozenset()
+    _accessors = set()  # type: Set[str]
     _deprecations = frozenset(
         ['asobject', 'base', 'data', 'flags', 'itemsize', 'strides'])