!17871 clean part of warning code in dataset.

From: @anzhengqi
Reviewed-by: @liucunwei,@jonyguo
Signed-off-by: @liucunwei

mindspore/dataset/engine/datasets.py

@@ -2912,9 +2912,15 @@ class _ToDevice:
         self._to_device.Send()
 
     def stop_send(self):
+        """
+        send stop send signal to pipeline, it is used when end of sequence is sent at the epoch end.
+        """
         self._to_device.StopSend()
 
     def continue_send(self):
+        """
+        send continue send signal to pipeline, it is used when end of sequence is sent at the epoch end.
+        """
         self._to_device.ContinueSend()
 
     def get_data_info(self):

mindspore/dataset/engine/iterators.py

@@ -67,7 +67,7 @@ class Iterator:
         self._col_names = None
 
         # create a copy of tree and work on it.
-        self._ori_dataset = dataset
+        self.__ori_dataset = dataset
 
         self.ir_tree, self.dataset = dataset.create_ir_tree()
 
@@ -125,8 +125,8 @@ class Iterator:
         if not data:
             if self.__index == 0:
                 logger.warning("No records available.")
-            if self._ori_dataset.dataset_size is None:
-                self._ori_dataset.dataset_size = self.__index
+            if self.__ori_dataset.dataset_size is None:
+                self.__ori_dataset.dataset_size = self.__index
             raise StopIteration
         self.__index += 1
         return data