fixup! Fix mypy error message in pandas/tests/indexes/test_numeric.py …

Author: grigoriosgiann

pandas/tests/indexes/common.py

@@ -31,7 +31,7 @@
 class Base:
     """ base class for index sub-class tests """
 
-    _holder: Optional[Type[Index]] = None
+    _holder = None  # type: Optional[Type[Index]]
     _compat_props = ["shape", "ndim", "size", "nbytes"]
 
     def test_pickle_compat_construction(self):