private void TestRoundTrip(string expected, GeoJsonCoordinateReferenceSystem crs)
        {
            var json = crs.ToJson();
            Assert.AreEqual(expected, json);

            var rehydrated = BsonSerializer.Deserialize<GeoJsonCoordinateReferenceSystem>(json);
            Assert.AreEqual(expected, rehydrated.ToJson());
        }
 // constructor
 /// <summary>
 /// Initializes a new instance of the <see cref="GeoJsonObject{TCoordinates}"/> class.
 /// </summary>
 /// <param name="args">The additional args.</param>
 protected GeoJsonObject(GeoJsonObjectArgs <TCoordinates> args)
 {
     if (args != null)
     {
         _boundingBox = args.BoundingBox;
         _coordinateReferenceSystem = args.CoordinateReferenceSystem;
         _extraMembers = args.ExtraMembers;
     }
 }