code: def quote_for_pydot(string):
      
      if isinstance(string, int):
          string = str(string)
      escaped_str = QUOTE_RE.sub(r'\\"', string)
      return u'"{}"'.format(escaped_str)
docs: takes a string (or int) and encloses it with "-chars. if the string
      contains "-chars itself, they will be escaped.