python code in tutorial "file input and output using xml and yaml files"

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Hello, I am new to openCV. I'm following the tutorials "File Input and Output using XML and YAML files ".

I encountered a problem when i execute the python code there. I cannot get the same result as the tutorial,

########################################################
Traceback (most recent call last):
  File "file_input_output.py", line 156, in <module>
    main(sys.argv)
  File "file_input_output.py", line 78, in main
    s.write('image1.jpg','Awesomeness')
cv2.error: OpenCV(4.3.0-pre) /home/ehuman/working_cv/opencv-master/modules/core/src/persistence_yml.cpp:251: error: (-5:Bad argument) Key names may only contain alphanumeric characters [a-zA-Z0-9], '-', '_' and ' ' in function 'writeScalar'
############################################################

It seems that the python binding here does not work well, could anybody help me explain the reason？