No scopes name and type info when loading the trace model

jit
1 
class LinearInLinear(nn.Module):
    def __init__(self):
        super(LinearInLinear, self).__init__()
        self.l = nn.Linear(3, 5)
        self.l1 = nn.Linear(5, 5)

    def forward(self, x):
        return self.l1(self.l(x + x))


class MyModel(nn.Module):
    def __init__(self):
        super(MyModel, self).__init__()
        self.l1 = LinearInLinear()
        self.l = LinearInLinear()

    def forward(self, input):
        x1 = self.l1(input)
        x2 = self.l(input)
        return x1 + x2 + x2
if __name__ == "__main__":
    dummy_input = (torch.rand(5, 3),)
    # with torch.onnx.set_training(model, False):
    trace = torch.jit.trace(model, dummy_input)
    # _optimize_trace(trace, torch._C._onnx.OperatorExportTypes.ONNX)
    trace.save("b.pt")
    print(trace.graph)
    for node in trace.graph.nodes():
        if node.kind() == "prim::Constant":
            continue
        print(list(node.outputs())[0].type().scalarType())
    print(type(trace))
    k = torch.jit.load("b.pt")
    print(type(k))
    print(k.graph)
    for node in k.graph.nodes():
        if node.kind() == "prim::Constant":
            continue
        print(node)
        output = list(node.outputs())[0]
        print(output.type().scalarType())
   the last

the last sentence produce the error below
RuntimeError: r ASSERT FAILED at /pytorch/aten/src/ATen/core/jit_type.h:142, please report a bug to PyTorch.