class Rails::SourceAnnotationExtractor::Annotation

def to_s(options = {})

Otherwise the string contains just line and text.
If +options+ has a flag :tag the tag is shown as in the example above.

[126] [TODO] This algorithm is simple and clearly correct, make it faster.

Returns a representation of the annotation that looks like this: 
def to_s(options = {})
  s = +"[#{line.to_s.rjust(options[:indent])}] "
  s << "[#{tag}] " if options[:tag]
  s << text
end