also save graph attributes (#78)

nnvm/src/pass/saveload_json.cc

@@ -199,6 +199,7 @@ Graph LoadJSON(Graph src) {
 // save a graph to json
 Graph SaveJSON(Graph src) {
   JSONGraph jgraph;
+  jgraph.attrs = src.attrs;
   std::unordered_map<Node*, uint32_t> node2index;
   jgraph.node_row_ptr.push_back(0);
   DFSVisit(src.outputs, [&node2index, &jgraph](const NodePtr& n) {

nnvm/tests/python/test_graph.py

@@ -11,6 +11,20 @@ def test_json_pass():
     g2 = ret.apply('LoadJSON')
     assert g2.apply('SaveJSON').json_attr('json') == ret.json_attr('json')
 
+
+def test_json_pass_with_attr():
+    x = sym.Variable('x')
+    y = sym.conv2d(data=x, name='conv', stride=(2,2))
+    g = graph.create(y)
+    g._set_json_attr('version', '0.1.0')
+    ret = g.apply('SaveJSON')
+    json_str = ret.json_attr('json')
+    print(json_str)
+    ret._set_json_attr('json', json_str)
+    g2 = ret.apply('LoadJSON')
+    assert g2.json_attr('version') == '0.1.0'
+
+
 def test_graph_json_attr():
     x = sym.Variable('x')
     y = sym.conv2d(data=x, name='conv', stride=(2,2))
@@ -129,6 +143,7 @@ def test_plan_memory():
 
 
 if __name__ == "__main__":
+    test_json_pass_with_attr()
     test_order_mutation_pass()
     test_graph_json_attr()
     test_json_pass()