xxxxx.xxxxx.creative.add
        ===================================
        创建一个创意

def add(self, adgroup_id, title, img_url, nick=None):
        '''xxxxx.xxxxx.creative.add
        ===================================
        创建一个创意'''
        request = TOPRequest('xxxxx.xxxxx.creative.add')
        request['adgroup_id'] = adgroup_id
        request['title'] = title
        request['img_url'] = img_url
        if nick!=None: request['nick'] = nick
        self.create(self.execute(request), fields=['success','result','success','result_code','result_message'], models = {'result':Creative})
        return self.result