fix split op in onnx (#645)

* fix expand op in onnx

* remove useless info

* fix split and add GatherND

* fix

* test revert

* update

* update

* reverse

* reverse expand

x2paddle/op_mapper/onnx2paddle/opset9/opset.py

@@ -793,6 +793,14 @@ class OpSet9():
         self.paddle_graph.add_layer(
             'paddle.multiply', inputs=inputs_dict, outputs=[node.name])
 
+    @print_mapping_info
+    def GatherND(self, node):
+        x = self.graph.get_input_node(node, idx=0, copy=True)
+        index = self.graph.get_input_node(node, idx=1, copy=True)
+        inputs = {'x': x.name, 'index': index.name}
+        self.paddle_graph.add_layer(
+            "paddle.gather_nd", inputs=inputs, outputs=[node.name])
+
     @print_mapping_info
     def Gather(self, node):
         val_x = self.graph.get_input_node(node, idx=0, copy=True)
@@ -1345,6 +1353,32 @@ class OpSet9():
         if split is None:
             split = len(node.outputs)
         axis = node.get_attr('axis', 0)
+        if split is None:
+            split_num = len(node.layer.output)
+            layer_attrs = {
+                'num_or_sections': split_num,
+                'axis': axis,
+            }
+            outputs_list = list()
+            for i in range(len(node.layer.output)):
+                if hasattr(node, 'index'):
+                    outputs_list.append("{}_p{}".format(node.layer_name, i))
+                else:
+                    outputs_list.append("{}".format(node.layer_name))
+            if split_num > 1:
+                self.paddle_graph.add_layer(
+                    'paddle.split',
+                    inputs={"x": val_x.name},
+                    outputs=outputs_list,
+                    **layer_attrs)
+            else:
+                self.paddle_graph.add_layer(
+                    "paddle.cast",
+                    inputs={"x": val_x.name},
+                    outputs=outputs_list,
+                    dtype=string(val_x.dtype))
+
+        else:
             layer_attrs = {
                 'num_or_sections': split,
                 'axis': axis,
@@ -1357,11 +1391,7 @@ class OpSet9():
                     for i in range(len(split)):
                         outputs_list.append("{}_p{}".format(node.layer_name, i))
             else:
-            if len(node.outputs) == 1:
                 outputs_list.append(node.name)
-            else:
-                for i in range(len(node.outputs)):
-                    outputs_list.append("{}_p{}".format(node.layer_name, i))
             self.paddle_graph.add_layer(
                 'paddle.split',
                 inputs={"x": val_x.name},