class_docstr: Key press event, delivered to key bindings.
  
  :param key_processor_ref: Weak reference to the `KeyProcessor`.
  :param arg: Repetition argument.
  :param key_sequence: List of `KeyPress` instances.
  :param previouskey_sequence: Previous list of `KeyPress` instances.
  :param is_repeat: True when the previous event was delivered to the same handler.
docstr: Add digit to the input argument.
  
  :param data: the typed digit as string
docstr_tok: ["Add","digit","to","the","input","argument",".",":","param","data",":","the","typed","digit","as","string"]
code: def append_to_arg_count(self, data: str) -> None:
      """
      Add digit to the input argument.
  
      :param data: the typed digit as string
      """
      assert data in "-0123456789"
      current = self._arg
  
      if data == "-":
          assert current is None or current == "-"
          result = data
      elif current is None:
          result = data
      else:
          result = f"{current}{data}"
  
      self.key_processor.arg = result
  
imports: from __future__ import annotations
  import weakref
  from asyncio import Task, sleep
  from collections import deque
  from typing import TYPE_CHECKING, Any, Generator
  from prompt_toolkit.application.current import get_app
  from prompt_toolkit.enums import EditingMode
  from prompt_toolkit.filters.app import vi_navigation_mode
  from prompt_toolkit.keys import Keys
  from prompt_toolkit.utils import Event
  from .key_bindings import Binding, KeyBindingsBase
label_desc: Use image node_id 9 for calling the KeyPressEvent obj's underlying member method code with example usage: obj.append_to_arg_count(data) without return types