class_docstr: A filter allowing to implement pass-through behaviour of keybindings.
  
  Prompt toolkit key processor dispatches only one event per binding match,
  which means that adding a new shortcut will suppress the old shortcut
  if the keybindings are the same (unless one is filtered out).
  
  To stop a shortcut binding from suppressing other shortcuts:
  - add the `pass_through` filter to list of filter, and
  - call `pass_through.reply(event)` in the shortcut handler.
code: def __call__(self):
      return not self._is_replying
  
imports: import ast
  import re
  import signal
  import sys
  from typing import Callable, Dict, Union
  from prompt_toolkit.application.current import get_app
  from prompt_toolkit.enums import DEFAULT_BUFFER, SEARCH_BUFFER
  from prompt_toolkit.key_binding import KeyPressEvent
  from prompt_toolkit.filters import Condition, Filter, emacs_insert_mode, has_completions
  from prompt_toolkit.filters import has_focus
  from prompt_toolkit.filters import Always, Never, has_selection, has_suggestion, vi_insert_mode, vi_mode
  from prompt_toolkit.layout.layout import FocusableElement
  from IPython.core.getipython import get_ipython
  from IPython.core.guarded_eval import _find_dunder, BINARY_OP_DUNDERS, UNARY_OP_DUNDERS
  from IPython.terminal.shortcuts import auto_suggest
  from IPython.utils.decorators import undoc
label_desc: Use image node_id 3 for calling the PassThrough obj's underlying member method code with example usage: obj.__call__() and returns: unknown