Helllo guys why i'm getting this error?

    raise ValueError("Expected singleton: %s" % self)
ValueError: Expected singleton: product.pricelist.item(8, 9)

this is the related code:

                    elif rule.compute_price == 'nettech':
                        if product.aed_is_true:
                            price_tempo = self.env['res.currency'].search([('name', '=', 'IRR')], limit=1).rate * product.aed_in_irr + product.sud2 + (((self.env['res.currency'].search([('name', '=', 'IRR')], limit=1).rate * product.aed_in_irr + product.sud2) * (product.sud-rule.product_sub) / 100)) or 0.0
                            price = round(price_tempo,-4)
                        elif not product.aed_is_true:
                            price = price