def get_tree(cls, parent=None):
        """
        :returns: A list of nodes ordered as DFS, including the parent. If
                  no parent is given, the entire tree is returned.
        """
        if parent:
            depth = parent.get_depth() + 1
            results = [parent]
        else:
            depth = 1
            results = []
        cls._get_tree_recursively(results, parent, depth)
        return results
:returns: A list of nodes ordered as DFS, including the parent. If
                  no parent is given, the entire tree is returned.