For Projection ticket: Unable to use Bson class query builder

I am using Bson queryFilter and projection() to solve the requirement of finding “title” by country name. However it is failing build phase when I run the project. It is not accepting “fieldName” in Bson object queryFilter and iterator() method.
I have attached screenshot where you can see the code snippet and build errors. Please help.

First, the fieldname is countries. And I believe eq operator will not be the best way as the parameter country can be comma separated multiple strings as well.

Please check the test file for more information on how the function will be called.