class_docstr: Context manager which Installs a SIGWINCH callback.
  (This signal occurs when the terminal size changes.)
code: def __init__(self, callback):
      self.callback = callback
      self.previous_callback = None
  
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 1 to create a new call_on_sigwinch object from inherited base classes: object with example: obj = call_on_sigwinch(callback)