Documentation property always null in CompletionItem

If I use the method RequestCompletion() I got a CompletionList with functions/methods. If I select a CompletionItem from this list the Documentation property is always null also for standard functions like print(). This is what I've tried:

` var actualCompletions = await _client.TextDocument.RequestCompletion(
new CompletionParams
{
TextDocument = @"path\to\script.py",
Position = (24, 9),
}, cancellationTokenSource.Token
);

            System.Threading.Thread.Sleep(1000);

            IEnumerable<CompletionItem> cmpltItems = actualCompletions?.Items;
            var cmpltItem = (cmpltItems?.FirstOrDefault(p => p.Label == "print"));
            if (cmpltItem != null)
            {
                Console.WriteLine(cmpltItem.Documentation);
            }`

No source file or test is named. Start by tracing TextDocument.RequestCompletion and how CompletionItem.Documentation is populated or deserialized, using the shown print() reproduction; done means the selected completion item exposes its documentation instead of null.