pub fn storage_key_for_standard_token_balance(
    token_contract: AccountTreeId,
    address: &Address,
) -> StorageKey {
    // We have different implementation of the standard ERC20 contract and native
    // eth contract. The key for the balance is different for each.
    let key = if token_contract.address() == &L2_BASE_TOKEN_ADDRESS {
        key_for_eth_balance(address)
    } else {
        key_for_erc20_balance(address)
    };

    StorageKey::new(token_contract, key)
}
Create a storage key to access the balance from supported token contract balances
core/lib/types/src/utils.rs