Iterate and get nested key from a BSON OrderedDocument

I'm trying to iterate and get the value from a nested BSON OrderedDocument. I tried this:

for post in cursor {
    if let Ok(item) = post {
        println!("{:?}", item.get("sentiment")); // get "kelas" inside "sentiment"
    }
}

for post in cursor {
    if let Ok(item) = post {
        for row in item.iter() {
            println!("{:?}", row);  // get ["sentiment"]["kelas"]
        }
    }
}