def group_lines
      @lines.rewind

      inList = false
      wantedType = wantedLevel = nil

      block = LineCollection.new
      group = nil

      while line = @lines.next
        if line.level == wantedLevel and line.type == wantedType
          group.add_text(line.text)
        else
          group = block.fragment_for(line)
          block.add(group)
          if line.type == Line::LIST
            wantedType = Line::PARAGRAPH
          else
            wantedType = line.type
          end
          wantedLevel = line.type == Line::HEADING ? line.param : line.level
        end
      end

      block.normalize
      block
    end
def group_lines
      @lines.rewind

      inList = false
      wantedType = wantedLevel = nil

      block = LineCollection.new
      group = nil

      while line = @lines.next
        if line.level == wantedLevel and line.type == wantedType
          group.add_text(line.text)
        else
          group = block.fragment_for(line)
          block.add(group)
          if line.type == Line::LIST
            wantedType = Line::PARAGRAPH
          else
            wantedType = line.type
          end
          wantedLevel = line.type == Line::HEADING ? line.param : line.level
        end
      end

      block.normalize
      block
    end
Return a block consisting of fragments which are
 paragraphs, list entries or verbatim text. We merge consecutive
 lines of the same type and level together. We are also slightly
 tricky with lists: the lines following a list introduction
 look like paragraph lines at the next level, and we remap them
 into list entries instead