optparse.OptionParser:
Class attributes:
standard_option_list : [Option]
list of standard options that will be accepted by all instances
of this parser class (intended to be overridden by subclasses).
bosco.ranking.Rankable:
Defines the interface for rankable objects like courses and categories.
bosco.ranking.Ranking:
A Ranking objects combines a scoreing strategy, a validation
strategy and a rankable object (course or category) and computes a
ranking.