contract Ownable is Context {
    address internal _owner; // 成都链安 // 声明变量_owner，存储合约所有者地址

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner); // 成都链安 // 声明合约所有者权限转移事件

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(_owner == _msgSender(), "Ownable: caller is not the owner"); // 成都链安 // 修饰器，要求被修饰函数的调用者必须为合约所有者
        _;
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address"); // 成都链安 // newOwner非零地址检查，避免合约所有者权限丢失
        emit OwnershipTransferred(_owner, newOwner); // 成都链安 // 触发OwnershipTransferred事件
        _owner = newOwner; // 成都链安 // 转移合约所有者权限至newOwner
    }
}
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address"); // 成都链安 // newOwner非零地址检查，避免合约所有者权限丢失
        emit OwnershipTransferred(_owner, newOwner); // 成都链安 // 触发OwnershipTransferred事件
        _owner = newOwner; // 成都链安 // 转移合约所有者权限至newOwner
    }
/**
 * @dev Transfers ownership of the contract to a new account (`newOwner`).
 * Can only be called by the current owner.
 */