odoo - stock picking package preparation -> get lot id for each line

test.py

picking_ids = line.package_preparation_id.picking_ids.ids
search_args = [
    ('picking_id', 'in', picking_ids),
    ('product_id', '=', line.product_id.id),
]
pack_items = self.env['stock.pack.operation'].search(search_args)
lots = []
for item in pack_items:
    lots.extend([x.lot_id.name for x in item.pack_lot_ids])