```\n// ABI encode calldata for `fillOrder`\nbytes memory fillOrderCalldata = abi.encodeWithSelector(\n    IExchangeCore(address(0)).fillOrder.selector,\n    order,\n    takerAssetFillAmount,\n    signature\n);\n\n(bool didSucceed, bytes memory returnData) = address(this).delegatecall(fillOrderCalldata);\n```\n