Created by: pkuyym

1. function name: https://github.com/PaddlePaddle/X2Paddle/blob/develop/x2paddle/core/graph.py#L102 Seems conflict with built-in 'print'.
2. function definition: https://github.com/PaddlePaddle/X2Paddle/blob/develop/x2paddle/op_mapper/onnx_op_mapper.py#L97 should be

def directly_map(self, node, name='', *args,  **kwargs):

3. need to handle Unicode string https://github.com/PaddlePaddle/X2Paddle/blob/develop/x2paddle/core/fluid_code.py#L31 https://github.com/PaddlePaddle/X2Paddle/blob/develop/x2paddle/core/fluid_code.py#L75