code: def duplicate_for_child(self, fd):
      self._fds.append(fd)
      return len(self._fds) - 1
  
file_path: catboost/contrib/tools/python3/src/Lib/multiprocessing/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 2 for calling the Popen obj's underlying member method code with example usage: obj.duplicate_for_child(fd) and returns: unknown