mypy fixup

Author: jbrockmendel

pandas/tests/io/parser/test_textreader.py

@@ -28,7 +28,7 @@
 #  either both-sets or both dicts, and the code assumes this is the case.
 #  But the default argument in its __init__ is None, so we have to pass these
 #  explicitly in tests.
-_na_value_kwargs = {"na_values": set(), "na_fvalues": set()}
+_na_value_kwargs: dict[str, set] = {"na_values": set(), "na_fvalues": set()}
 
 
 class TestTextReader: