Update app.py

app.py

@@ -26,7 +26,7 @@ def find_qsar_guid_from_prompt(prompt: str, qsar_guid_index: int) -> str:
     return possible_qsar_guids[qsar_guid_index]['key']
 
 @tool
-def qsartoolbox_qsar_model_tool(smiles:str, qsarModelGUID: str)-> Optional[str]:
+def qsartoolbox_qsar_model_tool(smiles:str, qsarModelGUID: str)-> str  | None:
     """This machine learning model serves as an interface for the QSAR Toolbox API, 
     allowing users to input SMILES strings and select a QSAR model to generate predictive values for various properties.