code: def start_output (self):
          
          super(DOTLogger, self).start_output()
          if self.has_part("intro"):
              self.write_intro()
              self.writeln()
          self.writeln(u"digraph G {")
          self.writeln(u"  graph [")
          self.writeln(u"    charset=\"%s\"," % self.get_charset_encoding())
          self.writeln(u"  ];")
          self.flush()
docs: Write start of checking info as DOT comment.