Laravel-mongodb: Unrecognized expression '$toString' in Aggregate.php

[rupendradhiman-kiwi]

I have issue on QA environment.
I am running a project using Docker. Docker configuration are same on all environments.
But the issue is only on QA.

We are trying to convert _id from object to string.

laravel.ERROR: Unrecognized expression '$toString'

[luisalvesjb]

tomou no cu

[brunoassiscarvalho]

This is about mongo version, in documentation $toString, only in version 4 above. I have the same problem, and I resolved with { $convert: { input: , to: "string" } }.