/// <summary>
/// Inserts default constructed children into collection and returns a span for the newly created range.
/// </summary>
/// <param name="count">Count of children that will be added.</param>
/// <returns></returns>
internal Span <IVisualNode> AddChildrenSpan(int count)
{
EnsureChildrenCreated(count);
return(_children.AddSpan(count));
}