code review related modifications to use with mypy validation

[vsitnik]

Could be an overkill. Perhaps there's no need in using @dataclass and stuff.
To run mypy validation do the following:

[ -f venv/bin/activate ] && source venv/bin/activate || python3 -m venv venv

which mypy || pip install mypy

mypy --pretty apollo_email_report/module/transcript.py
# Success: no issues found in 1 source file