A Fragment is a chunk of text, subclassed as a paragraph, a list entry, or verbatim text
This is a simple factory system that lets us associate fragement types (a string) with a subclass of fragment
# File rdoc/markup/simple_markup/fragments.rb, line 41 def Fragment.for(line) klass = TYPE_MAP[line.type] || raise("Unknown line type: '#{line.type.inspect}:' '#{line.text}'") return klass.new(line.level, line.param, line.flag, line.text) end