##### System information (version) <!-- Example - OpenCV => 4.3 - Operating System / Platform => Linux Ubuntu 18.04 LTS - Compiler => gcc version 7.4.0 --> ##### Detailed description <!-- the python code in tutorial "File input and output using xml and yaml files" does not work properly; --> ##### Issue submission checklist https://answers.opencv.org/question/228751/python-code-in-tutorial-file-input-and-output-using-xml-and-yaml-files/