class virtualThe base class for prioritizers. Defines methods for converting priority levels into 1) their corresponding code, and 2) their corresponding message tag.['a]prioritizer :object..end
method virtual code : 'a -> Priority.tp#code v to convert the priority level v to a priority
code with the prioritizer p.method virtual tag : 'a -> stringp#tag v to convert the priority level v to a message
tag with the prioritizer p.