!9641 fix getnext error in pynative mode

From: @chujinjin
Reviewed-by: @jjfeing,@limingqi107
Signed-off-by: @limingqi107

mindspore/train/dataset_helper.py

@@ -94,7 +94,8 @@ def connect_network_with_dataset(network, dataset_helper):
 
     if (hasattr(dataset_iter, "sink_size") and dataset_iter.sink_size == 1) \
             and (hasattr(dataset_iter, "sink_count") and dataset_iter.sink_count == 1) \
-        and context.get_context("device_target") == "Ascend":
+            and context.get_context("device_target") == "Ascend" \
+            and context.get_context("mode") == context.GRAPH_MODE:
 
         if not hasattr(dataset, '__network__'):
             dataset.__network__ = network
@@ -206,6 +207,7 @@ class DatasetHelper:
     def get_data_info(self):
         return self.iter.get_data_info()
 
+
 class _DatasetIter:
     """Base iter for dataset helper"""
 
@@ -286,6 +288,7 @@ class _DatasetIterGE(_DatasetIter):
 
         self.op = op
 
+
 class _DatasetIterPyNative(_DatasetIter):
     """Iter for MS(enable_loop_sink=False)."""
 
@@ -301,6 +304,7 @@ class _DatasetIterPyNative(_DatasetIter):
 
         self.op = op
 
+
 class _DatasetIterMSLoopSink(_DatasetIter):
     """Iter for context (device_target=Ascend)"""
 
@@ -354,6 +358,7 @@ class _DatasetIterPSLite(_DatasetIter):
 
 class _DatasetIterNormal:
     """Iter for normal(non sink) mode, feed the data from host."""
+
     def __init__(self, dataset, epoch_num=-1):
         self.dataset = dataset
         self.device_num = _get_device_num()