The class is a simple extension of dict, and adds an explicit attribute for the content of the root node of a tree. It makes the code much more readable with very small performance overhead. closes odoo/odoo#111946 X-original-commit: 8a01d74e5f7d035cfd05bc02596f075270e0fcf8 Signed-off-by: Raphael Collet <rco@odoo.com>