class Treetop::Runtime::SyntaxNode

def write_dot(io)
  io.puts "node#{dot_id} [label=\"'#{text_value}'\"];"
  if nonterminal? then
    elements.each do
      |x|
      io.puts "node#{dot_id} -> node#{x.dot_id};"
      x.write_dot(io)
    end
  end
end