pub trait CopyBytes: BlockContainer {
    // Required method
    fn copy_bytes_at(&self, offset: usize, dst: &mut [u8]);
    // Provided method
    fn copy_bytes(&self, dst: &mut [u8]) { ... }
}pub trait CopyBytes: BlockContainer {
    // Required method
    fn copy_bytes_at(&self, offset: usize, dst: &mut [u8]);
    // Provided method
    fn copy_bytes(&self, dst: &mut [u8]) { ... }
}