Add filename as a output file for this DAG node.

    @param filename: output filename to add

def add_output_file(self, filename):
    """
    Add filename as a output file for this DAG node.

    @param filename: output filename to add
    """
    if filename not in self.__output_files:
      self.__output_files.append(filename)
      if not isinstance(self.job(), CondorDAGManJob):
        if self.job().get_universe() == 'grid':
          self.add_output_macro(filename)