from tensorflow.core.example import example_pb2
tf_example = example_pb2.Example()
tf_example.features.feature['article'].bytes_list.value.extend(['test test testing'])

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-1-7fc29de54f13> in <module>()
      1 from tensorflow.core.example import example_pb2
      2 tf_example = example_pb2.Example()
----> 3 tf_example.features.feature['article'].bytes_list.value.extend(['test test testing'])

TypeError: 'test test testing' has type str, but expected one of: bytes