code: def backend_exists(self):
      # TODO: if IB is available we should suggestion mvapich
      mpiname_exists = shutil.which("mpiname")
      exists = False
      if not mpiname_exists:
          warnings.warn(
              "mpiname does not exist, mvapich is not installed properly"
          )
      else:
          results = subprocess.check_output("mpiname", shell=True)
          mpiname_results = results.decode("utf-8").strip()
          if "MVAPICH2-GDR" in mpiname_results:
              exists = True
          else:
              warnings.warn(
                  f"Expected MVAPICH2-GDR as return for mpiname but received {mpiname_results}"
              )
      return exists
  
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 2 for calling the MVAPICHRunner obj's underlying member method code with example usage: obj.backend_exists() and returns: exists