code: def write_concrete_dag(self):
      
      if not self.__dag_file_path:
        raise CondorDAGError, "No path for DAG file"
      try:
        dagfile = open( self.__dag_file_path, 'w' )
      except:
        raise CondorDAGError, "Cannot open file " + self.__dag_file_path
      for node in self.__nodes:
        node.write_job(dagfile)
        node.write_vars(dagfile)
        if node.get_category():
          node.write_category(dagfile)
        if node.get_priority():
          node.write_priority(dagfile)
        node.write_pre_script(dagfile)
        node.write_post_script(dagfile)
        node.write_input_files(dagfile)
        node.write_output_files(dagfile)
      for node in self.__nodes:
        node.write_parents(dagfile)
      for category in self.__maxjobs_categories:
        self.write_maxjobs(dagfile, category)
      dagfile.close()
docs: Write all the nodes in the DAG to the DAG file.