You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: prodash.rs
    path of file: ./repos/pants/src/rust/engine/ui/src/instance
    
    the code of the file until where you have to start completion: // Copyright 2020 Pants project contributors (see CONTRIBUTORS.md).
// Licensed under the Apache License, Version 2.0 (see LICENSE).

use std::collections::HashMap;
use std::fmt;
use std::sync::mpsc;
use std::time::Duration;
use std::time::SystemTime;
use std::time::UNIX_E
    
    pub fn teardown(mut self) -> BoxFuture<'static, ()> {
        // Drop all tasks to clear the Tree. The call to shutdown will render a final "Tick" with the
        // empty Tree, which will clear the screen.
        self.tasks_to_display.clear();
        self.executor
            .clone()
            .spawn_blocking(
                move || self.handle.shutdown_and_wait(),
                |e| fatal_log!("Failed to teardown UI: {e}"),
            )
            .boxed()
    }