code: def poll(self, flag=os.WNOHANG):
      if self.returncode is None:
          from multiprocess.connection import wait
  
          timeout = 0 if flag == os.WNOHANG else None
          if not wait([self.sentinel], timeout):
              return None
          try:
              self.returncode = forkserver.read_signed(self.sentinel)
          except (OSError, EOFError):
              # This should not happen usually, but perhaps the forkserver
              # process itself got killed
              self.returncode = 255
  
      return self.returncode
  
file_path: multiprocess/pypy3.9/multiprocess/popen_forkserver.py
imports: import io
  import os
  from .context import reduction, set_spawning_popen
  from .None import forkserver
  from .None import popen_fork
  from .None import spawn
  from .None import util
label_desc: Use image node_id 4 for calling the Popen obj's underlying member method code with example usage: obj.poll(flag) and returns: self, None