# File lib/rdoc/markup.rb, line 233
  def convert(str, op)
    lines = str.split(/\r?\n/).map { |line| Line.new line }
    @lines = Lines.new lines

    return "" if @lines.empty?
    @lines.normalize
    assign_types_to_lines
    group = group_lines
    # call the output formatter to handle the result
    #group.each { |line| p line }
    group.accept @am, op
  end