fix math lrn op numerical problem

Author: lei-Qiao

tf2onnx/onnx_opset/math.py

@@ -255,14 +255,15 @@ def version_1(cls, ctx, node, **kwargs):
         if depth_radius:
             size = depth_radius.i * 2 + 1
         else:
+            # by default, depth_radius is 5 in tensorflow
             size = 5 * 2 + 1
 
         node.set_attr("size", size)
         node.set_attr("alpha", size * node.get_attr("alpha").f)
 
-        ctx.insert_new_node_on_input(node, "Transpose", node.input[0], perm=[0, 3, 1, 2])
+        ctx.insert_new_node_on_input(node, "Transpose", node.input[0], perm=constants.NHWC_TO_NCHW)
         op_name = utils.make_name(node.name)
-        ctx.insert_new_node_on_output("Transpose", node.output[0], perm=[0, 2, 3, 1], name=op_name)
+        ctx.insert_new_node_on_output("Transpose", node.output[0], perm=constants.NCHW_TO_NHWC, name=op_name)
 
 
 @tf_op(["MatMul", "BatchMatMul"])