code: def item_exist(self, campaign_id, item_id, nick=None):
          '''xxxxx.xxxxx.adgroups.item.exist
          ===================================
          判断在一个推广计划中是否已经推广了一个商品'''
          request = TOPRequest('xxxxx.xxxxx.adgroups.item.exist')
          request['campaign_id'] = campaign_id
          request['item_id'] = item_id
          if nick!=None: request['nick'] = nick
          self.create(self.execute(request))
          return self.resulf item_exist(self, campaign_id, item_id, nick=None):
          '''xxxxx.xxxxx.adgroups.item.exist
          ===================================
          判断在一个推广计划中是否已经推广了一个商品'''
          request = TOPRequest('xxxxx.xxxxx.adgroups.item.exist')
          request['campaign_id'] = campaign_id
          request['item_id'] = item_id
          if nick!=None: request['nick'] = nick
          self.create(self.execute(request))
          return self.result
docs: xxxxx.xxxxx.adgroups.item.exist
          ===================================
          判断在一个推广计划中是否已经推广了一个商品