add rename fix

src/nested_pandas/utils/utils.py

@@ -30,8 +30,9 @@ def count_nested(df, nested, by=None, join=True) -> NestedFrame:
     if by is None:
         field_to_len = df[nested].nest.fields[0]
         counts = (
-            df[nested].nest.to_lists().apply(lambda x: len(x[field_to_len]), axis=1).rename(f"n_{nested}")
+            df[nested].nest.to_lists().apply(lambda x: len(x[field_to_len]), axis=1)  # .rename(f"n_{nested}")
         )
+        counts.name = f"n_{nested}"  # update name directly (rename causes issues downstream)
     else:
         # this may be able to be sped up using tolists() as well
         counts = df[nested].apply(lambda x: x[by].value_counts(sort=False))