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: iter.rs
    path of file: ./repos/bee/bee-storage/bee-storage-sled/src/access
    
    the code of the file until where you have to start completion: // Copyright 2021 IOTA Stiftung
// SPDX-License-Identifier: Apache-2.0

//! Iter access operations.

use std::marker::PhantomData
    
    fn unpack_key_value(key: &[u8], value: &[u8]) -> (BlockId, Block) {
        (
            // Unpacking from storage is fine.
            BlockId::unpack_unverified(key).unwrap(),
            // Unpacking from storage is fine.
            Block::unpack_unverified(value).unwrap(),
        )
    }