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: builder.rs
    path of file: ./repos/ethers-rs/ethers-middleware/tests/it
    
    the code of the file until where you have to start completion: use ethers_core::{rand::thread_rng, type
    
async fn build_raw_middleware_stack() {
    let (provider, mock) = Provider::mocked();

    let signer = LocalWallet::new(&mut thread_rng());
    let address = signer.address();
    let escalator = GeometricGasPrice::new(1.125, 60u64, None::<u64>);

    let provider = provider
        .wrap_into(|p| GasEscalatorMiddleware::new(p, escalator, Frequency::PerBlock))
        .wrap_into(|p| GasOracleMiddleware::new(p, GasNow::new()))
        .wrap_into(|p| SignerMiddleware::new(p, signer))
        .wrap_into(|p| NonceManagerMiddleware::new(p, address));

    // push a response
    mock.push(U64::from(12u64)).unwrap();
    let block: U64 = provider.get_block_number().await.unwrap();
    assert_eq!(block.as_u64(), 12);

    provider.get_block_number().await.unwrap_err();

    // 2 calls were made
    mock.assert_request("eth_blockNumber", ()).unwrap();
    mock.assert_request("eth_blockNumber", ()).unwrap();
    mock.assert_request("eth_blockNumber", ()).unwrap_err();
}