add code sample for pandas-dev#40073

Author: simonjayhawkins

bisect/40073.py

@@ -0,0 +1,9 @@
+import pandas as pd
+
+print(pd.__version__)
+d1 = pd.DataFrame([("a",)], columns=["id"], dtype="string")
+d2 = pd.DataFrame([("b",)], columns=["id"], dtype="string")
+result = d1.merge(d2, on="id", how="right")
+dtype = result.dtypes["id"]
+print(dtype)
+assert isinstance(dtype, pd.StringDtype)