NewCurriculum returns a collection of language tracks.

NewHomework decorates a problem set with some additional data based on the user's system.

HWAll represents all items in the collection.

HWNew represents newly fetched problems.

HWNotSubmitted represents problems that have not yet been submitted for review.

HWUpdated represents problems where files have been added.

TrackActive represents an active track.

TrackInactive represents an inactive track.

Curriculum is a collection of language tracks.

Homework is a collection of problems that were fetched from the APIs.

Item is a problem that has been fetched from the APIs.

HWFilter is used to categorize homework items.

Status is the status of a track (active/inactive).

SummaryOption allows selective display of summary items.