Why does it did not get the correct computation for tax?  here my codes:

class sale_order(osv.osv):
    _inherit = "sale.order"
    
    def _amount_line_tax(self, cr, uid, line, context=None):
        val = 0.0
        for c in self.pool.get('account.tax').compute_all(cr, uid, line.tax_id, ((line.price_unit * (1-(line.discount or 0.0)/100.0)) *(1-(line.bo_disc or 0.0)/100.0)* (1-(line.cod_disc or 0.0)/100.0)) , line.product_uom_qty, line.product_id, line.order_id.partner_id)['taxes']:
            val += c.get('amount', 0.0)
          
        return val
    
    def _amount_all(self, cr, uid, ids, field_name, arg, context=None):
        cur_obj = self.pool.get('res.currency')
        res = {}
        for order in self.browse(cr, uid, ids, context=context):
            res[order.id] = {
                'amount_untaxed': 0.0,
                'amount_tax': 0.0,
                'amount_total': 0.0,
            }
            val = val1 = 0.0
            cur = order.pricelist_id.currency_id
            for line in order.order_lines:
                val1 += line.price_subtotal
                val += self._amount_line_tax(cr, uid, line, context=context)
            res[order.id]['amount_tax'] = cur_obj.round(cr, uid, cur, val)
            netsvc.Logger().notifyChannel("-----------------222..",netsvc.LOG_INFO, '' +'' + str(res[order.id]['amount_tax']))
            res[order.id]['amount_untaxed'] = cur_obj.round(cr, uid, cur, val1)
            res[order.id]['amount_total'] = res[order.id]['amount_untaxed'] + res[order.id]['amount_tax']
        return res
       
       
    def _get_order(self, cr, uid, ids, context=None):
        result = {}
        for line in self.pool.get('sale.order.line').browse(cr, uid, ids, context=context):
            result[line.order_id.id] = True
        return result.keys()  
     
    _column = {
               'discount': fields.float('Discount 1(%)', digits_compute= dp.get_precision('Discount'), readonly=True, states={'draft': [('readonly', False)]}),
               'disc_amount' : fields.float('Disccount Amount', digits=(10,7)),
               'bo_disc' :fields.float('Discount 2(%)', digits=(10,2)),
               'bo_amount':fields.float('BO Amount', digits=(10,7)),
               'cod_disc' :fields.float('Discount 3(%)', digits=(10,2)),
               'cod_amount' :fields.float('COD Amont', digits=(10,7)),
               
        'amount_untaxed': fields.function(_amount_all, digits_compute=dp.get_precision('Account'), string='Untaxed Amount',
            store={
                'sale.order': (lambda self, cr, uid, ids, c={}: ids, ['order_line'], 10),
                'sale.order.line': (_get_order, ['price_unit', 'tax_id', 'discount', 'product_uom_qty'], 10),
            },
            multi='sums', help="The amount without tax.", track_visibility='always'),
        'amount_tax': fields.function(_amount_all, digits_compute=dp.get_precision('Account'), string='Taxes',
            store={
                'sale.order': (lambda self, cr, uid, ids, c={}: ids, ['order_line'], 10),
                'sale.order.line': (_get_order, ['price_unit', 'tax_id', 'discount', 'product_uom_qty'], 10),
            },
            multi='sums', help="The tax amount."),
        'amount_total': fields.function(_amount_all, digits_compute=dp.get_precision('Account'), string='Total',
            store={
                'sale.order': (lambda self, cr, uid, ids, c={}: ids, ['order_line'], 10),
                'sale.order.line': (_get_order, ['price_unit', 'tax_id', 'discount', 'product_uom_qty'], 10),
            },
            multi='sums', help="The total amount."),
               }
    
    
sale_order()