public Tree GetParent(Tree node)
{
if (node is IHasParent)
{
return(node.Parent());
}
if (nodesToParents == null)
{
nodesToParents = new IdentityDictionary <Tree, Tree>();
}
if (nodesToParents.Count == 0)
{
FillNodesToParents(root, null);
}
Tree parent;
nodesToParents.TryGetValue(node, out parent);
return(parent);
}
