!12916 [MD][bugfix] Fix map object pickle issue

From: @xiefangqi
Reviewed-by: @liucunwei,@pandoublefeng
Signed-off-by: @liucunwei

mindspore/train/dataset_helper.py

@@ -102,24 +102,24 @@ def connect_network_with_dataset(network, dataset_helper):
             and context.get_context("mode") == context.GRAPH_MODE \
             and ms_role != "MS_WORKER":
 
-        if not hasattr(dataset, '__network__'):
-            dataset.__network__ = network
-        network = dataset.__network__
+        if not hasattr(dataset_iter, '__network__'):
+            dataset_iter.__network__ = network
+        network = dataset_iter.__network__
 
         dataset_types, dataset_shapes = dataset_helper.get_data_info()
         dataset_types = [pytype_to_dtype(x) for x in dataset_types]
 
         key = str(dataset_types) + str(dataset_shapes)
-        if hasattr(dataset, '__network_manage__') and key in dataset.__network_manage__:
-            network = dataset.__network_manage__[key]
+        if hasattr(dataset_iter, '__network_manage__') and key in dataset_iter.__network_manage__:
+            network = dataset_iter.__network_manage__[key]
         else:
             if _need_to_full():
                 device_num = _get_device_num()
                 dataset_shapes = _to_full_shapes(dataset_shapes, device_num)
             network = _DataWrapper(network, dataset_types, dataset_shapes, dataset.__transfer_dataset__.queue_name)
-            dataset.__network_manage__ = dataset.__network_manage__ if hasattr(
-                dataset, '__network_manage__') else dict()
-            dataset.__network_manage__[key] = network
+            dataset_iter.__network_manage__ = dataset_iter.__network_manage__ if hasattr(
+                dataset_iter, '__network_manage__') else dict()
+            dataset_iter.__network_manage__[key] = network
 
         return network