1.Generate demo checkpoint and savedmodel
```
python simple_model.py --saved_model_dir=xxx --checkpoint_dir=xxx
```
if not set saved_model_dir, the default dir is '/tmp/saved_model',
if not set checkpoint_dir, the default dir is '/tmp/checkpoint/1'.
```
python simple_model.py
```

2.Set `saved_model_dir` and `checkpoint_dir` to model_config which defined in demo.cc.
static const char* model_config = "{
    ...
    "checkpoint_dir": "/tmp/ckpt/", 
    "savedmodel_dir": "/tmp/saved_model/" 
  } ";
Attention: checkpoint_dir here should be the parent checkpoint dir, 
for example '/tmp/checkpoint/1', set checkpoint_dir as '/tmp/checkpoint'.

3.Build demo and run
bazel build //serving/processor/tests:demo
bazel-bin/serving/processor/tests/demo

