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: a.rs
    path of file: ./repos/embassy/examples/boot/application/stm32l4/src/bin
    
    the code of the file until where you have to start completion: #![no_std]
#![no_main]

#[cfg(featu
    
async fn main(_spawner: Spawner) {
    let p = embassy_stm32::init(Default::default());
    let flash = Flash::new_blocking(p.FLASH);
    let flash = Mutex::new(BlockingAsync::new(flash));

    let mut button = ExtiInput::new(p.PC13, p.EXTI13, Pull::Up);

    let mut led = Output::new(p.PB14, Level::Low, Speed::Low);
    led.set_high();

    let config = FirmwareUpdaterConfig::from_linkerfile(&flash, &flash);
    let mut magic = AlignedBuffer([0; WRITE_SIZE]);
    let mut updater = FirmwareUpdater::new(config, &mut magic.0);
    button.wait_for_falling_edge().await;
    let mut offset = 0;
    for chunk in APP_B.chunks(2048) {
        let mut buf: [u8; 2048] = [0; 2048];
        buf[..chunk.len()].copy_from_slice(chunk);
        updater.write_firmware(offset, &buf).await.unwrap();
        offset += chunk.len();
    }
    updater.mark_updated().await.unwrap();
    led.set_low();
    cortex_m::peripheral::SCB::sys_reset();
}