remove use of sql direct for delete, just use import line as needed to avoid circular import

loan.py

@@ -90,11 +90,11 @@ def loan(id):
         loan = Loan.query.get(id)
         try:
             if 'delete' in request.form:
+                from main import Book_Loan_Link
+
                 st.SetMessage( f"Successfully deleted (id={loan.id}, who={loan.firstnames} {loan.surname})" )
-                # fall back to direct sql because loan.py is imported before Book_Loan_Link exists
-                with db.engine.connect() as conn:
-                    conn.exec_driver_sql( f"delete from book_loan_link where loan_id = {loan.id}" )
-                loan = Loan.query.filter(Loan.id==id).delete()
+                Book_Loan_Link.query.filter(Loan.id==id).delete()
+                Loan.query.filter(Loan.id==id).delete()
             if 'submit' in request.form:
                 st.SetMessage( f"Successfully Updated Loan (id={id})" )
                 loan.firstnames = request.form['firstnames']