Odoo, how get supplier Price value from supplierinfo, in custom module?

Question

I'm a odoo 13 user (not developer). In a custom module which add products lines in Purchase Order, I need to add: product_id, name, price_unit , taxes_id. product_id, name, taxes_id values are available in product.product and I can get its value with this code:

'product_id': product.id,
'name': product.name,
'taxes_id': product.supplier_taxes_id,

but 'price_unit' value is in product.supplierinfo (it's supplier price) and if I use code:

'price_unit':  supplierinfo.price

I have error: NameError: name 'supplierinfo' is not defined

What's my mistake? How I can get Supplier Price value from product.supplierinfo and assign it to 'price_unit'???

I'm not developer and I don't know how create code, please any suggestion it's appreciated with code. Thanks Below complete code:

    def _add_product(self, product, qty, price):
        corresponding_line = self.order_line.filtered(lambda r: r.product_id.id == product.id)
        if corresponding_line:
            corresponding_line[0].product_qty += float(qty)
            corresponding_line[0].price_unit = float(price) or supplierinfo.price
        else:
            self.order_line += self.order_line.new({
                'product_id': product.id,
                'product_qty': qty,
                'date_planned': fields.Datetime.to_string(datetime.datetime.now() - dateutil.relativedelta.relativedelta(months=1)),
                'name': product.name,
                'product_uom': product.uom_id.id,
                'price_unit': float(price) or supplierinfo.price,       
                'taxes_id': product.supplier_taxes_id,
            })
        return True

Answer 1

Try with this code,

    def _add_product(self, product, qty, price):
        corresponding_line = self.order_line.filtered(lambda r: r.product_id.id == product.id)
        # My Cust Start
        supplierinfo = product.mapped('seller_ids')[:1]
        # My Cust End
        if corresponding_line:
            corresponding_line[0].product_qty += float(qty)
            corresponding_line[0].price_unit = float(price) or supplierinfo.price
        else:
            self.order_line += self.order_line.new({
                'product_id': product.id,
                'product_qty': qty,
                'date_planned': fields.Datetime.to_string(datetime.datetime.now() - dateutil.relativedelta.relativedelta(months=1)),
                'name': product.name,
                'product_uom': product.uom_id.id,
                'price_unit': float(price) or supplierinfo.price,       
                'taxes_id': product.supplier_taxes_id,
            })
        return True

Thanks