aggregation pipeline with multiple unwinds and replaceWith

Program.cs

using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Entities;
using MongoDB.Entities.Core;
using System.Linq;

namespace StackOverFlow
{
    public class OptionMenu : Entity
    {
        public OptionMenuSubject[] subjects { get; set; }
    }

    public class OptionMenuSubject
    {
        public OptionMenuItem[] items { get; set; }
    }

    public class OptionMenuItem
    {
        public ObjectId id { get; set; }
        public string name { get; set; }
    }

    public static class Program
    {
        private static void Main()
        {
            new DB("test", "localhost");

            var pipeline = new Template<OptionMenu, OptionMenuItem>(@"
            [
                {
                    $match: {
                        '<subjects.items>._id': <item_id>
                    }
                },
                {
                    $unwind: '$<subjects>'
                },
                {
                    $unwind: '$<subjects.items>'
                },
                {
                    $match: {
                        '<subjects.items>._id': <item_id>
                    }
                },
                {
                    $replaceWith: '$<subjects.items>'
                }
            ]")

            .Path(m => m.subjects[0].items)
            .Tag("item_id", "ObjectId('5e6eaef8ae35a418f4f6dbd4')")
            .Path(m => m.subjects);

            OptionMenuItem item = DB.Aggregate(pipeline)
                                    .ToList()
                                    .SingleOrDefault();
        }
    }
}