def to_s
      # Sorted by filename and line number.
      #
      #     FC123: My rule name: foo/recipes/default.rb
      @warnings.map do |w|
        ["#{w.rule.code}: #{w.rule.name}: #{w.match[:filename]}",
         w.match[:line].to_i]
      end.sort do |x, y|
        x.first == y.first ? x[1] <=> y[1] : x.first <=> y.first
      end.map { |w| "#{w.first}:#{w[1]}" }.uniq.join("\n")
    end
def to_s
      # Sorted by filename and line number.
      #
      #     FC123: My rule name: foo/recipes/default.rb
      @warnings.map do |w|
        ["#{w.rule.code}: #{w.rule.name}: #{w.match[:filename]}",
         w.match[:line].to_i]
      end.sort do |x, y|
        x.first == y.first ? x[1] <=> y[1] : x.first <=> y.first
      end.map { |w| "#{w.first}:#{w[1]}" }.uniq.join("\n")
    end
Returns a string representation of this review. This representation is
 liable to change.