code: def add_input_file(self, filename):
      
      if filename not in self.__input_files:
        self.__input_files.append(filename)
        if not isinstance(self.job(), CondorDAGManJob):
          if self.job().get_universe() == 'grid':
            self.add_input_macro(filename)
docs: Add filename as a necessary input file for this DAG node.
  
      @param filename: input filename to add