Finding documents with the sync API in Rust is very slow.

Actual behaviour:
When executing collection.find() with the exact same parameters in Rust (mongodb::sync subpackage) and in Python3, Rust needs 19.8 seconds to query 250K documents, while Python3 needs only 1.1 seconds.

Expected behaviour:

Rust should need slightly less time than Python.

Steps to reproduce:

Populate a collection with a few thousand documents, and execute the same find query once in Rust and once in Python3 that returns a few thousand documents as well.

I have created a GitHub repository with sample code and three scripts to reduce reproduction time: https://github.com/RandomApfel/mongo-rust-slow-issue-reproduction