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: signer.rs
    path of file: ./repos/krill/src/commons/crypto/signing/signers/pkcs11
    
    the code of the file until where you have to start completion: use std::{
    convert::{TryFrom, TryInto},
    marker::PhantomData,
    path::Path,
    sync::{Arc, R
    
    fn default() -> Self {
        // These values are backward compatible with the hard-coded values
        // used by Krill before they were made configurable for #1018.
        // See: https://github.com/NLnetLabs/krill/issues/1018
        Self {
            cka_modifiable: None,
            cka_private: Some(true),
        }
    }