报错如下

Error: Could not parse /Users/zhangnan/blockchain/test_merge/node_modules/@openzeppelin/contracts/token/ERC20/ERC20.sol for extracting its imports: ParserError: missing ';' at '{' (158:18)
at getDependencies (/usr/local/lib/node_modules/truffle-flattener/index.js:44:11)
at dependenciesDfs (/usr/local/lib/node_modules/truffle-flattener/index.js:64:24)

最简单的openzeppelin erc20 token代码

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.2;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

contract MyToken is ERC20 {
    constructor() ERC20("MyToken", "MTK") {}
}

使用命令

truffle-flattener TestOpenzeppelin.sol > test_merge2.sol

怎么解决这个问题？