sequence

Solve how to order list of records
Limit number of writes

   sequence = fields.Integer('Sequence')
   # keep id order
   cls._order.insert(0, ('sequence', 'ASC'))

   def order_sequence(tables):
       table, _ = tables[None]
       return [
           Case((table.sequence == Null, 0), else_=1),
           table.sequence]

Mixin: https://bugs.tryton.org/issue5105