class_docstr: Context manager which Installs a SIGWINCH callback.
  (This signal occurs when the terminal size changes.)
code: def __enter__(self):
      self.previous_callback = signal.signal(
          signal.SIGWINCH, lambda *a: self.callback()
      )
  
imports: from __future__ import unicode_literals
  import fcntl
  import os
  import signal
  import threading
  import time
  from prompt_toolkit.terminal.vt100_input import InputStream
  from prompt_toolkit.utils import DummyContext, in_main_thread
  from prompt_toolkit.input import Input
  from .base import EventLoop, INPUT_TIMEOUT
  from .callbacks import EventLoopCallbacks
  from .inputhook import InputHookContext
  from .posix_utils import PosixStdinReader
  from .utils import TimeIt
  from .select import AutoSelector, Selector, fd_to_int
label_desc: Use image node_id 2 for calling the call_on_sigwinch obj's underlying member method code with example usage: obj.__enter__() without return types