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: unbound_key.rs
    path of file: ./repos/ring/src/aead
    
    the code of the file until where you have to start completion: // Copyright 2015-2021 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, 
    
    fn from(okm: hkdf::Okm<&'static Algorithm>) -> Self {
        let mut key_bytes = [0; MAX_KEY_LEN];
        let key_bytes = &mut key_bytes[..okm.len().key_len];
        let algorithm = *okm.len();
        okm.fill(key_bytes).unwrap();
        Self {
            inner: LessSafeKey::new_(algorithm, key_bytes).unwrap(),
        }
    }