title: how to solve this transaction error in mlab? [MongoError: Transaction numbers are ... support document-level locking]
body: <p>I'm trying to do a simple transaction using <code>mongoose</code>. It worked totally fine on <code>MongoDB Atlas</code>, but in <code>mlab</code> I got such an error: <code>MongoError: Transaction numbers are only allowed on storage engines that support document-level locking</code>. I did some research, but didn't really find any resources regarding <code>mlab</code> and <code>document-level locking</code>. 
  Does anyone know how to solve this problem?</p>