fix call to preserve type fn

statemodify/xdd.py

@@ -255,6 +255,7 @@ def convert(self):
                 months=self.months,
                 output_path=self.output_path,
                 id_subset=self.id_subset,
+                preserve_string_dtype=self.preserve_string_dtype,
             )
             for file in tqdm(self.xdd_files)
         )
@@ -269,6 +270,7 @@ def _parse_file(
         months: list[str],
         output_path: str,
         id_subset: Union[None, list[str]],
+        preserve_string_dtype: bool,
     ):
         data = []
         with open(file) as f:
@@ -290,7 +292,7 @@ def _parse_file(
         if id_subset is not None:
             df = df[df["structure_id"].isin(id_subset)]
 
-        if self.preserve_string_dtype is False:
+        if preserve_string_dtype is False:
             df = df.astype(self.field_dtypes)
 
         df.to_parquet(f"{output_path}/{Path(file).stem}.parquet")