Bugfix issue2485

[zheng-ningxin]

Fix the bug mentioned in issue 2485.
In addition, to pass the merge check pipeline, I also fix several pylint warnings.

I visualize the resnet18, resnet34, mobilev2, googlenet, squeezenet1_1 by TorchModuleGraph for testing, and it works fine.

[chicm-ms]

would you add a test case with shared nn.Module in test_graph_utils.py and/or test_model_speedup.py?

[zheng-ningxin]

Fix the bug by adding a function called _expand_module_node without touching compressor.py. However, it does give us a reminder that you should be careful when using the name obtained by find_successor to get the corresponding module from the model.

[QuanluZhang]

for the previous implementation, this while loop will never end?

[zheng-ningxin]

In the previous implementation, it does have a directed loop in the graph: relu->liner2, liner2->relu. However, it will not loop forever, because it will fail on "the assert len(nodes) == 1".
In the previous implementation, relu will have two successors (liner2, linear3).

[QuanluZhang]

looks great!