class_docstr: An environment for running on clusters managed by the LSF resource manager.
  
  It is expected that any execution using this ClusterEnvironment was executed
  using the Job Step Manager i.e. ``jsrun``.
  
  This plugin expects the following environment variables:
  
  ``LSB_JOBID``
    The LSF assigned job ID
  
  ``LSB_DJOB_RANKFILE``
    The OpenMPI compatible rank file for the LSF job
  
  ``JSM_NAMESPACE_LOCAL_RANK``
    The node local rank for the task. This environment variable is set by ``jsrun``
  
  ``JSM_NAMESPACE_SIZE``
    The world size for the task. This environment variable is set by ``jsrun``
  
  ``JSM_NAMESPACE_RANK``
    The global rank for the task. This environment variable is set by ``jsrun``
docstr: A helper for getting the main address.
  
  The main address is assigned to the first node in the list of nodes used for the job.
docstr_tok: ["A","helper","for","getting","the","main","address",".","The","main","address","is","assigned","to","the","first","node","in","the","list","of","nodes","used","for","the","job","."]
code: def _get_main_address(self) -> str:
      """A helper for getting the main address.
  
      The main address is assigned to the first node in the list of nodes used for the job.
  
      """
      hosts = self._read_hosts()
      return hosts[0]
  
imports: import logging
  import os
  import socket
  from typing import Dict, List
  from typing_extensions import override
  from lightning.fabric.plugins.environments.cluster_environment import ClusterEnvironment
  from lightning.fabric.utilities.cloud_io import get_filesystem
label_desc: Use image node_id 15 for calling the LSFEnvironment obj's underlying member method code with example usage: obj._get_main_address() and returns: hosts