done

lib/python3.11/site-packages/pandas/tests/strings/__init__.py

@@ -0,0 +1,23 @@
+import numpy as np
+
+import pandas as pd
+
+
+def is_object_or_nan_string_dtype(dtype):
+    """
+    Check if string-like dtype is following NaN semantics, i.e. is object
+    dtype or a NaN-variant of the StringDtype.
+    """
+    return (isinstance(dtype, np.dtype) and dtype == "object") or (
+        dtype.na_value is np.nan
+    )
+
+
+def _convert_na_value(ser, expected):
+    if ser.dtype != object:
+        if ser.dtype.na_value is np.nan:
+            expected = expected.fillna(np.nan)
+        else:
+            # GH#18463
+            expected = expected.fillna(pd.NA)
+    return expected