Mapstache.Utf8Grid.CreateGraphics C# (CSharp) Метод

        public Graphics CreateGraphics()
        {
            return Graphics.FromImage(_bitmap);
        }

 public void TestMethodWithPartiallyFillTileReturnsEmptyStringId()
 {
     using (var utfGrid = new Utf8Grid(1,1,1,1))
     {
         var graphics = utfGrid.CreateGraphics();
         var brush = Utf8Grid.CreateBrush(5);
         graphics.FillRectangle(brush, 0, 0, 10, 10);
         var json = utfGrid.CreateUtfGridJson();
         Assert.AreEqual(2, utfGrid.Keys.Count);
         Assert.AreEqual("", utfGrid.Keys[0]);
         Assert.AreEqual("5", utfGrid.Keys[1]);
     }
 }