resolve error

app.py

@@ -49,6 +49,15 @@ def sql_engine(query: str) -> str:
         return f"Error: {str(e)}"
 
 def query_sql(user_query: str) -> str:
+    """
+    Converts a natural language query into an SQL statement and executes it.
+
+    Args:
+        user_query (str): A question or request in natural language to be converted into SQL.
+    
+    Returns:
+        str: The execution result from the database.
+    """
     schema_info = (
         "The database has a table named 'receipts' with the following schema:\n"
         "- receipt_id (INTEGER, primary key)\n"