function assetPrice()
    public
    view
    override
    returns (uint) {
      // ...
      address[] memory vaults = kerosineManager.getVaults();
      uint numberOfVaults = vaults.length;
      for (uint i = 0; i < numberOfVaults; i++) {
        Vault vault = Vault(vaults[i]);
        // ...
                * vault.assetPrice() * 1e18
        // ...
      }
function getKeroseneValue(
    uint id
  )
    public
    view
    returns (uint) {
      uint numberOfVaults = vaultsKerosene[id].length();
      for (uint i = 0; i < numberOfVaults; i++) {
        Vault vault = Vault(vaultsKerosene[id].at(i));
        if (keroseneManager.isLicensed(address(vault))) {
          usdValue = vault.getUsdValue(id);
        }
        //...
  }
function isLicensed(
    address vault
  )
    return vaults.contains(vault);
kerosineManager.add(address(ethVault));
kerosineManager.add(address(wstEth));
