Hi,

Please try this code:vendor_ids = fields.Many2many('product.supplierinfo', 'Vendors', compute='_compute_vendor_ids')
vendor = fields.Many2one('product.supplierinfo', 'Vendors', domain="[('id', 'in', vendor_ids)]")

@api.depends('product_id')

def _compute_vendor_ids(self):

for record in self:

    if record.product_id:

        record.product_desc = record.product_id.name

        value = [data.id for data in record.product_id.seller_ids if data]

        if value:

            record.vendor_ids = value

Hope it helps