class_docstr: Describe the environment inside which the job is running.
  This includes job id, number of GPUs available, ...
  
  This class can only be instantiated from a running submitit job.
  
  @plugin-dev: default implementation look for information into environment variables.
  Override _env to map environment variable to each property.
code: def _usr_sig(cls) -> tp.Any:
      name = "SIG" + cls.USR_SIG
      out = getattr(signal, name, None)
      if out is None:
          raise RuntimeError(
              f"Unknown signal {name}, you may need to unset or update env var {_PREEMPT_SIG_ENV} (Eg: USR2)"
          )
      return out
  
imports: import os
  import signal
  import socket
  import sys
  import time
  import types
  import typing
  from pathlib import Path
  from .None import logger, utils
  from .utils import DelayedSubmission, JobPaths
label_desc: Use image node_id 18 for calling the JobEnvironment obj's underlying member method code with example usage: obj._usr_sig(cls) and returns: out