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: vp.rs
    path of file: ./repos/namada/crates/tests/src/vm_host_env
    
    the code of the file until where you have to start completion: use std::cell::RefCell;
use std::collections::BTreeSet;

use namada::core::address::{self, Address};
use namada::core::storage::{self, Key, TxIndex};
use namada::gas::TxGasMeter;
use namada::ledger::gas::VpGasMeter;
use namada::ledger::storage::mockdb::MockDB;
use namada::ledger::storage::testing::TestState;
use namada::tx::data::TxType;
use nama
    
    pub fn with<T>(f: impl Fn(&mut TestVpEnv) -> T) -> T {
        ENV.with(|env| {
            let mut env = env.borrow_mut();
            let mut env = env
                .as_mut()
                .expect(
                    "Did you forget to initialize the ENV? (e.g. call to \
                     `vp_host_env::init()`)",
                )
                .as_mut();
            f(&mut env)
        })
    }