pub trait CacheReporter: Send + Sync {
fn on_validate_start(&self) -> usize;
fn on_validate_complete(&self, index: usize);
fn on_download_start(&self) -> usize;
fn on_download_progress(&self, index: usize, progress: u64, total: Option<u64>);
fn on_download_completed(&self, index: usize);
}