# File sipper/sdp/sdp.rb, line 152
    def clone
      ret = Sdp.new

      [ :v, :o, :s, :i, :u, :e, :p, :c, :b, :z, :k, :t, :r, :a].each do |attr|
        unless @sa[attr].nil?
          ret.session_lines = {} unless ret.session_lines
          ret.session_lines[attr] = @sa[attr]
        end
      end
      
      # media lines
      if @ma
        ret.media_lines = []
        @ma.each do |ma|
          currattr = {}
          [ :m, :i, :c, :b, :k, :a ].each do |attr|
            unless ma[attr].nil?
              currattr[attr] = ma[attr]
            end
          end
          ret.media_lines << currattr
        end
      end

      return ret
    end