code: def _run_grid_multiprocess(self, func, iterables):
          ''' running case with mutil process to support selenium grid-mode(multiple web) and appium grid-mode(multiple devices). 
          @param func:  function object
          @param iterables:  iterable objects
          '''
          multiprocessing.freeze_support()
          pool = multiprocessing.Pool()        
          pool_tracers = pool.map(func, iterables)
          pool.close()
          pool.join()
          
          # 传递给 pool.map的 实例对象，内存地址发生变化， 因此，这里在运行结束后，重新定义 self.tracers 
          self.tracers = dict(zip(self._default_devices, pool_tracers)f _run_grid_multiprocess(self, func, iterables):
          ''' running case with mutil process to support selenium grid-mode(multiple web) and appium grid-mode(multiple devices). 
          @param func:  function object
          @param iterables:  iterable objects
          '''
          multiprocessing.freeze_support()
          pool = multiprocessing.Pool()        
          pool_tracers = pool.map(func, iterables)
          pool.close()
          pool.join()
          
          # 传递给 pool.map的 实例对象，内存地址发生变化， 因此，这里在运行结束后，重新定义 self.tracers 
          self.tracers = dict(zip(self._default_devices, pool_tracers))
docs: running case with mutil process to support selenium grid-mode(multiple web) and appium grid-mode(multiple devices). 
          @param func:  function object
          @param iterables:  iterable objects