My task is when onchangeof invoice_line_tax_id from customer invoice line then it result should be

result=new_total+invoice_line_tax_id ,But i cannt get the result when the onchange of invoice_line_tax_id is changes.How to resolve this issue.Please need a help

This is the onchange method 

#def onchange_tax_id(self,cr,uid,ids,invoice_line_tax_id,context=None):

from osv import osv,fields

class account_new(osv.osv):
    
    _inherit='account.invoice.line'

    def onchange_schemid(self,cr,uid,ids,price_unit,quantity,context=None):
            if price_unit:
                amount_new=price_unit*quantity
                return {'value':{'new_total':amount_new}}
            return {}
        
    def onchange_tax_id(self,cr,uid,ids,invoice_line_tax_id,context=None):
        a=self.pool.get('account.invoice.line').read(cr,uid,['new_total'],context=context)
        b=self.pool.get('account.tax').read(cr,uid,['invoice_line_tax_id'],context=context)
        if invoice_line_tax_id:
                val1=a[0]['new_total']
                val2=b[0]['invoice_line_tax_id']
                amount_with_tax=val1+val2
                return {'value':{'new_with_tax':amount_with_tax}}
        return {}
        
    _columns={
              'new_total': fields.integer('Gross Amount', required=True),
              'new_with_tax':fields.float('Amount')
              }
    
    
account_new()

EDIT------------

.xml  file

<xpath expr="/form/sheet/notebook/page[1]/field[1]/tree/field[11]" position="inside">
                        <field name="invoice_line_tax_id" on_change="onchange_tax_id(invoice_line_tax_id)"/>
                    </xpath>

.py file

class account_new(osv.osv):
    
    _inherit='account.invoice.line'

    def onchange_schemid(self,cr,uid,ids,price_unit,quantity,context=None):
            if price_unit:
                amount_new=price_unit*quantity
                return {'value':{'new_total':amount_new}}
            return {}
        
    def onchange_tax_id(self,cr,uid,ids,invoice_line_tax_id,context=None):
        
         acc_tax_obj = self.pool.get('account.tax')
         line_tax = invoice_line_tax_id
         for val in acc_tax_obj.browse(cr, uid, line_tax);
             amount = val.amount
             return {'value':{'new_with_tax':amount}}

But this onchange is not working------------