http://www.dcs.fmph.uniba.sk/~lukotka/PTS/2021/typingtest.py
https://realpython.com/python-type-checking/
http://www.dcs.fmph.uniba.sk/~lukotka/UDML/du2.htm
http://www.dcs.fmph.uniba.sk/~lukotka/OOAM/2019/du3.htm