# File rdoc/dot/dot.rb, line 188
        def initialize( params = {}, option_list = GRAPH_OPTS )
            super( params, option_list )
            @nodes = params['nodes'] ? params['nodes'] : []
            @dot_string = 'subgraph'
        end

# File rdoc/dot/dot.rb, line 198
        def << ( thing )
            @nodes << thing
        end

# File rdoc/dot/dot.rb, line 194
        def each_node
            @nodes.each{ |i| yield i }
        end

# File rdoc/dot/dot.rb, line 206
        def pop
            @nodes.pop
        end

# File rdoc/dot/dot.rb, line 202
        def push( thing )
            @nodes.push( thing )
        end

# File rdoc/dot/dot.rb, line 210
        def to_s( t = '' )
          hdr = t + "#{@dot_string} #{@name} {\n"

          options = @options.to_a.collect{ |name, val|
            val && name != 'label' ?
            t + $tab + "#{name} = #{val}" :
              name ? t + $tab + "#{name} = \"#{val}\"" : nil
          }.compact.join( "\n" ) + "\n"

          nodes = @nodes.collect{ |i|
            i.to_s( t + $tab )
          }.join( "\n" ) + "\n"
          hdr + options + nodes + t + "}\n"
        end