message: Adding `--implicit-optional` to mypy
diff: @@ -109,4 +109,4 @@ PYTHONPATH=./tests git ls-files tests/ python/ | grep -e '\.py$' | xargs python
  echo "$CHECK_DELIMITER"
  echo "-- Python types"
  -git ls-files python/ | grep -e '\.py$' | xargs mypy
  +git ls-files python/ | grep -e '\.py$' | xargs mypy --implicit-optional
  