```\nif (\_fee > 0) {\n address feeReceiver = \_feeRecipient == address(0) ? msg.sender : \_feeRecipient;\n (bool feePaymentSuccess, ) = feeReceiver.call{ value: \_fee }("");\n if (!feePaymentSuccess) {\n revert FeePaymentFailed(feeReceiver);\n }\n```\n