'returns a recordset of all the children computed recursively, and sorted by sequence. Ready for the printing'

def _get_children_by_order(self):

    res = self
    children = self.search([('parent_id', 'in', self.ids)], order='sequence    ASC')
    if children:
        for child in children:
            res += child._get_children_by_order()
    return res
