public TestHierarchyModel <T> AddChild(T value)
        {
            var node = new TestHierarchyModel <T>(value)
            {
                Parent = this
            };

            _children.Add(node);
            return(node);
        }
 public bool RemoveChild(TestHierarchyModel <T> node)
 {
     return(_children.Remove(node));
 }