Update src/ansys/dpf/core/data_sources.py

Co-authored-by: Paul Profizi <[email protected]>

Author: luisaFelixSalles

src/ansys/dpf/core/data_sources.py

@@ -403,7 +403,7 @@ def add_file_path_for_specified_result(
         filepath: Union[str, os.PathLike],
         key: Optional[str] = "",
         result_key: Optional[str] = "",
-    ):
+    ) -> None:
         """Add a file path for a specified result file key to the data sources.
 
         This method can be used when results files with different keys (extensions) are