code: def add_export(self, key, var):
      self.exports[key.strip()] = var.strip()
  
imports: import os
  import sys
  import shutil
  import subprocess
  import warnings
  from shlex import split
  from abc import ABC, abstractmethod
  from ..utils import logger
  from .constants import PDSH_MAX_FAN_OUT, MVAPICH_TMP_HOSTFILE
label_desc: Use image node_id 4 for calling the MultiNodeRunner obj's underlying member method code with example usage: obj.add_export(key, var) without return types