code: def update(self, distributor_id, grade_id, session, trade_type=None):
          '''taobao.fenxiao.cooperation.update 更新合作关系等级
          
          供应商更新合作的分销商等级'''
          request = TOPRequest('taobao.fenxiao.cooperation.update')
          request['distributor_id'] = distributor_id
          request['grade_id'] = grade_id
          if trade_type!=None: request['trade_type'] = trade_type
          self.create(self.execute(request, session), fields=['is_success'])
          return self.is_succesf update(self, distributor_id, grade_id, session, trade_type=None):
          '''taobao.fenxiao.cooperation.update 更新合作关系等级
          
          供应商更新合作的分销商等级'''
          request = TOPRequest('taobao.fenxiao.cooperation.update')
          request['distributor_id'] = distributor_id
          request['grade_id'] = grade_id
          if trade_type!=None: request['trade_type'] = trade_type
          self.create(self.execute(request, session), fields=['is_success'])
          return self.is_success
docs: taobao.fenxiao.cooperation.update 更新合作关系等级
          
          供应商更新合作的分销商等级