I have a list here and I trying to mapped the brand field. May I know how can I mapped this appended list?
Ex.[Chanel, Vuitton, Vuitton, Celine]
 I wanted Vuitton returned 1 data only

 ai_list = []
        for ai in ai_record:
            for ail in ai.invoice_line_ids:
                ai_list.append({  'partner_id': partner_id.name,
                                  'transaction_date': ai.date_invoice, 
                                  'invoice_number': ai.number, 
                                  'brand': ai.brand, // how to use mapped() here
                                  'net_value': ai.residual, })
        return ai_list