Code review comment for lp:~gary/launchpad/bug164196-3

Per our IRC discussion, I recommend providing a status enum, rather than just is_omitted. The values could include PENDING, SENT, SKIPPED.

I believe ResultSets support slicing, so it might be clearer in the doctest to get a ResultSet and then slice it.

However, the branch as it stands is a worthwhile improvement, so I'll approve it.