'Check whether Tax Rate is not entered twice for same Tax Type'

def check_item_tax(self):

    check_list = []
    for d in self.get(u'taxes'):
        if d.tax_type:
            account_type = frappe.db.get_value(u'Account', d.tax_type, u'account_type')
            if (account_type not in [u'Tax', u'Chargeable', u'Income    Account', u'Expense    Account']):
                frappe.throw(_(u'Item    Tax    Row    {0}    must    have    account    of    type    Tax    or    Income    or    Expense    or    Chargeable').format(d.idx))
            elif (d.tax_type in check_list):
                frappe.throw(_(u'{0}    entered    twice    in    Item    Tax').format(d.tax_type))
            else:
                check_list.append(d.tax_type)
