fix TypeError: log() takes exactly 0 positional arguments (1 given)

[OuHangKresnik]

Traceback (most recent call last): File "trial.py", line 4, in graph = taso.load_onnx('/disk2/woodpecker-model-zoo/tensorflow/model_for_taso.onnx') File "/disk2/ouhang.oh/miniconda/envs/taso/lib/python3.6/site-packages/taso-0.1.0-py3.6-linux-x86_64.egg/taso/init.py", line 494, in load_onnx outputs = xf_operators[op.op_type](op, graph, tensors, model.graph.initializer) File "/disk2/ouhang.oh/miniconda/envs/taso/lib/python3.6/site-packages/taso-0.1.0-py3.6-linux-x86_64.egg/taso/init.py", line 188, in _log outputs = graph.log(tensors[op.input[0]]) File "taso/_cython/core.pyx", line 211, in taso.core.PyGraph.log TypeError: log() takes exactly 0 positional arguments (1 given)