官网定义原生执行操作MongoDB的文档如下

execute ($collection, $bulk)
collection：表示当前查询的集合
bulk：是一个\MongoDB\Driver\BulkWrite对象

以下是测试代码

$data = [
            'name' => 'Tome',
           'age' => 20
];

$bulk = new \MongoDB\Driver\BulkWrite();
$bulk->insert($data);

Db::execute('demo', $bulk);

返回错误信息：
message: think\db\connector\Mongo::execute(): Argument #1 ($bulk) must be of type MongoDB\Driver\BulkWrite, string given
file: vendor/topthink/think-orm/src/db/connector/Mongo.php
line: 316