Set the level\'s root of the given depth to index

        :param depth: the depth level
        :type depth: int
        :param index: the new root index
        :type index: QtCore.QModelIndex
        :returns: None
        :rtype: None
        :raises: None

def set_root(self, depth, index):
        """Set the level\'s root of the given depth to index

        :param depth: the depth level
        :type depth: int
        :param index: the new root index
        :type index: QtCore.QModelIndex
        :returns: None
        :rtype: None
        :raises: None
        """
        if depth < len(self._levels):
            self._levels[depth].set_root(index)