code: def add_var_opt(self, opt, short=False):
      
      if opt not in self.__var_opts:
        self.__var_opts.append(opt)
        macro = self.__bad_macro_chars.sub( r'', opt )
        if short:
          self.add_short_opt(opt,'$(macro' + macro + ')')
        else:
          self.add_opt(opt,'$(macro' + macro + ')')
docs: Add a variable (or macro) option to the condor job. The option is added
      to the submit file and a different argument to the option can be set for
      each node in the DAG.
      @param opt: name of option to add.