public async Task <IList <CompletionItem> > GetCompletion(CompletionTriggerInfo trigger, int position)
        {
            var groups = await CompletionService.GetCompletionItemGroupsAsync(
                GetCurrentDocument(), position, trigger).ConfigureAwait(false);

            if (groups == null)
            {
                return(new CompletionItem[0]);
            }
            return(groups.SelectMany(t => t.Items).ToArray());
        }