code: def backward_delete_char(event: E) -> None:
      """
      Delete the character behind the cursor.
      """
      if event.arg < 0:
          # When a negative argument has been given, this should delete in front
          # of the cursor.
          deleted = event.current_buffer.delete(count=-event.arg)
      else:
          deleted = event.current_buffer.delete_before_cursor(
              count=event.arg
          )
  
      if not deleted:
          event.app.output.bell()
  
imports: from __future__ import annotations
  from typing import Callable, TypeVar, Union, cast
  from prompt_toolkit.document import Document
  from prompt_toolkit.enums import EditingMode
  from prompt_toolkit.key_binding.key_bindings import Binding, key_binding
  from prompt_toolkit.key_binding.key_processor import KeyPress, KeyPressEvent
  from prompt_toolkit.keys import Keys
  from prompt_toolkit.layout.controls import BufferControl
  from prompt_toolkit.search import SearchDirection
  from prompt_toolkit.selection import PasteMode
  from .completion import display_completions_like_readline, generate_completions
label_desc: Use image node_id 21 for calling a global function with example usage: backward_delete_char(event) without return types