Method truncate

crates/vm/src/stdlib/_io.rs:354–358

(&mut self, pos: Option<usize>)

        }

        fn truncate(&mut self, pos: Option<usize>) -> usize {
            let pos = pos.unwrap_or_else(|| self.tell() as usize);
            self.cursor.get_mut().truncate(pos);
            pos
        }
    }

    fn check_closed(file: &PyObject, vm: &VirtualMachine) -> PyResult<()> {