private void MergeEmptyChildren(CoverNode <T> node)
{
if (node.HasChildren() && node.AreExistingChildrenEmpty())
{
node.MergeEmptyChildren();
}
if (node.IsRootNode() || !node.IsEmpty() || node.HasChildren())
{
return;
}
MergeEmptyChildren(node.GetParent());
}