generator: remove unused param, small clean up

Remove mod_obj parameter from _guess_groups() not used since
Iaa4e9a806e79032ce1675b46a6b7a7628c3eff89

Do not need to initialize opt_type before try/except because the try
will initialize opt_type or system will exit.

Always use multi-line string syntax for docstrings

Change-Id: I3185a14e3cef48584bdcb406f01e066c6d928bf5
Merge "generator: remove unused param, small clean up"