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: delay.rs
    path of file: ./repos/rCore/crate/memory/src/memory_set/handler
    
    the code of the file until where you have to start completion: use super::*;

#[derive(Debug, Clone)]
pub struct Delay<T: FrameAllocator> {
    allocator: T,
}

impl<T: FrameAllocator> MemoryHandler for Delay<T> {
    fn box_clone(&self) -> Box<dyn MemoryHandler> {
        Box::new(sel
    
    fn unmap(&self, pt: &mut dyn PageTable, addr: VirtAddr) {
        let entry = pt.get_entry(addr).expect("failed to get entry");
        if entry.present() {
            self.allocator.dealloc(entry.target());
        }

        // PageTable::unmap requires page to be present
        entry.set_present(true);
        pt.unmap(addr);
    }