you want to make a custom calculation with the price, according to conditions you must multiply by a factor. Example:  if it is tax 10, then you must multiply the price by 0.847
if it is tax 2, it must be multiplied by the predetermined factor.
then with the new values, the tax calculation is performed normally.
What is happening to me with the code, is that it does not respect the tax code (filter: if line_tax.tipo_afectacion_igv.code in ["10"]:  ), if it enters the conditions it is the value for all the calculations of the tax. Each calculation should be differentiated for each tax.

when it enters the condition of tax 10, it takes the value of 0.847 and uses it to calculate all the taxes, without respecting the condition : price_unit* factorTAX if line_tax.tipo_afectacion_igv.code in ["10"] else price_unit*FactorDEFAULT

code:

@api.multi
def get_taxes_values(self):#para calcular el valor de los impuestos.
    tax_grouped = {}
        for line in self.invoice_line_ids:
            if len(line.invoice_line_tax_ids)>0:
                for line_tax in line.invoice_line_tax_ids:
                    if line_tax.tipo_afectacion_igv.code in ["10"]:
                        price_unit = line.price_unit  
                        taxes=line.invoice_line_tax_ids.compute_all(price_unit* factorTAX if line_tax.tipo_afectacion_igv.code in ["10"] else price_unit*FactorDEFAULT, self.currency_id, line.quantity, line.product_id, self.partner_id)['taxes']

                    for tax in taxes: 
                        val = self._prepare_tax_line_vals(line, tax)
                        key = self.env['account.tax'].browse(tax['id']).get_grouping_key(val)

                        if key not in tax_grouped:
                            tax_grouped[key] = val
                        else:
                            tax_grouped[key]['amount'] += val['amount']
                        tax_grouped[key]['base'] += val['base']

        return tax_grouped