[CodeStyle][py2] remove the `next` method for python2 compatibility (PEP 3114) (#47728)

python/paddle/fluid/dataloader/dataloader_iter.py

@@ -354,10 +354,6 @@ class _DataLoaderIterSingleProcess(_DataLoaderIterBase):
 
             self._thread = None
 
-    # python2 compatibility
-    def next(self):
-        return self.__next__()
-
     def _try_shutdown_all(self):
         if not self._shutdown:
             try:
@@ -854,10 +850,6 @@ class _DataLoaderIterMultiProcess(_DataLoaderIterBase):
             if in_profiler_mode():
                 trace_event.end()
 
-    # python2 compatibility
-    def next(self):
-        return self.__next__()
-
     def _on_output_batch(self):
         for _ in range(len(self._places)):
             self._batches_outstanding -= 1

python/paddle/fluid/reader.py

@@ -152,15 +152,6 @@ class DataLoaderBase:
     def __call__(self):
         return self
 
-    def next(self):
-        '''
-        Get the next item in the DataLoader object. This method
-        should not be called by users directly. It is used for
-        implementing iterator protocol of Python 2.x inside
-        PaddlePaddle framework.
-        '''
-        return self.__next__()
-
     def __iter__(self):
         raise NotImplementedError()