code: def _readline(fd):
      """Read one line.  May block forever if no newline is read."""
      reader = io.FileIO(fd, mode="rb", closefd=False)
      return reader.readline()
  
imports: from test.support import verbose, reap_children
  from test.support.import_helper import import_module
  import errno
  import os
  import pty
  import tty
  import sys
  import select
  import signal
  import socket
  import io
  import unittest
  import warnings
label_desc: Use image node_id 2 for calling a global function with example usage: _readline(fd) and returns: reader