You only need to do this if you change the grammar file Demo.g4.
Only once, get the JAR for antlr:
curl -o antlr-4.13.1-complete.jar https://www.antlr.org/download/antlr-4.13.1-complete.jar
To run it:
java -jar antlr-4.13.1-complete.jar -Werror -no-listener -visitor -Dlanguage=Python3 -o demo Demo.g4
This is also provided in the shell script antlr4.sh
poetry install
poetry shell