code: def load_emacs_bindings() -> KeyBindingsBase:
      """
      Some e-macs extensions.
      """
      # Overview of Readline emacs commands:
      # http://www.catonmat.net/download/readline-emacs-editing-mode-cheat-sheet.pdf
      key_bindings = KeyBindings()
      handle = key_bindings.add
  
      insert_mode = emacs_insert_mode
  
      @handle("escape")
      def _esc(event: E) -> None:
          """
          By default, ignore escape key.
  
          (If we don't put this here, and Esc is followed by a key which sequence
          is not handled, we'll insert an Escape character in the input stream.
          Something we don't want and happens to easily in emacs mode.
          Further, people can always use ControlQ to do a quoted insert.)
          """
          pass
  
      handle("c-a")(get_by_name("beginning-of-line"))
      handle("c-b")(get_by_name("backward-char"))
      handle("c-delete", filter=insert_mode)(get_by_name("kill-word"))
      handle("c-e")(get_by_name("end-of-line"))
      handle("c-f")(get_by_name("forward-char"))
      handle("c-left")(get_by_name("backward-word"))
      handle("c-right")(get_by_name("forward-word"))
      handle("c-x", "r", "y", filter=insert_mode)(get_by_name("yank"))
      handle("c-y", filter=insert_mode)(get_by_name("yank"))
      handle("escape", "b")(get_by_name("backward-word"))
      handle("escape", "c", filter=insert_mode)(
          get_by_name("capitalize-word")
      )
      handle("escape", "d", filter=insert_mode)(
          get_by_name("kill-word")
      )
      handle("escape", "f")(get_by_name("forward-word"))
      handle("escape", "l", filter=insert_mode)(
          get_by_name("downcase-word")
      )
      handle("escape", "u", filter=insert_mode)(
          get_by_name("uppercase-word")
      )
      handle("escape", "y", filter=insert_mode)(get_by_name("yank-pop"))
      handle("escape", "backspace", filter=insert_mode)(
          get_by_name("backward-kill-word")
      )
      handle("escape", "\\", filter=insert_mode)(
          get_by_name("delete-horizontal-space")
      )
  
      handle("c-home")(get_by_name("beginning-of-buffer"))
      handle("c-end")(get_by_name("end-of-buffer"))
  
      handle("c-_", save_before=(lambda e: False), filter=insert_mode)(
          get_by_name("undo")
      )
  
      handle(
          "c-x",
          "c-u",
          save_before=(lambda e: False),
          filter=insert_mode,
      )(get_by_name("undo"))
  
      handle("escape", "<", filter=~has_selection)(
          get_by_name("beginning-of-history")
      )
      handle("escape", ">", filter=~has_selection)(
          get_by_name("end-of-history")
      )
  
      handle("escape", ".", filter=insert_mode)(
          get_by_name("yank-last-arg")
      )
      handle("escape", "_", filter=insert_mode)(
          get_by_name("yank-last-arg")
      )
      handle("escape", "c-y", filter=insert_mode)(
          get_by_name("yank-nth-arg")
      )
      handle("escape", "#", filter=insert_mode)(
          get_by_name("insert-comment")
      )
      handle("c-o")(get_by_name("operate-and-get-next"))
  
      # ControlQ does a quoted insert. Not that for vt100 terminals, you have to
      # disable flow control by running ``stty -ixon``, otherwise Ctrl-Q and
      # Ctrl-S are captured by the terminal.
      handle("c-q", filter=~has_selection)(get_by_name("quoted-insert"))
  
      handle("c-x", "(")(get_by_name("start-kbd-macro"))
      handle("c-x", ")")(get_by_name("end-kbd-macro"))
      handle("c-x", "e")(get_by_name("call-last-kbd-macro"))
  
      @handle("c-n")
      def _next(event: E) -> None:
          "Next line."
          event.current_buffer.auto_down()
  
      @handle("c-p")
      def _prev(event: E) -> None:
          "Previous line."
          event.current_buffer.auto_up(count=event.arg)
  
      def handle_digit(c: str) -> None:
          """
          Handle input of arguments.
          The first number needs to be preceded by escape.
          """
  
          @handle(c, filter=has_arg)
          @handle("escape", c)
          def _(event: E) -> None:
              event.append_to_arg_count(c)
  
      for c in "0123456789":
          handle_digit(c)
  
      @handle("escape", "-", filter=~has_arg)
      def _meta_dash(event: E) -> None:
          """"""
          if event._arg is None:
              event.append_to_arg_count("-")
  
      @handle(
          "-",
          filter=Condition(lambda: get_app().key_processor.arg == "-"),
      )
      def _dash(event: E) -> None:
          """
          When '-' is typed again, after exactly '-' has been given as an
          argument, ignore this.
          """
          event.app.key_processor.arg = "-"
  
      @Condition
      def is_returnable() -> bool:
          return get_app().current_buffer.is_returnable
  
      # Meta + Enter: always accept input.
      handle("escape", "enter", filter=insert_mode & is_returnable)(
          get_by_name("accept-line")
      )
  
      # Enter: accept input in single line mode.
      handle(
          "enter", filter=insert_mode & is_returnable & ~is_multiline
      )(get_by_name("accept-line"))
  
      def character_search(buff: Buffer, char: str, count: int) -> None:
          if count < 0:
              match = buff.document.find_backwards(
                  char, in_current_line=True, count=-count
              )
          else:
              match = buff.document.find(
                  char, in_current_line=True, count=count
              )
  
          if match is not None:
              buff.cursor_position += match
  
      @handle("c-]", Keys.Any)
      def _goto_char(event: E) -> None:
          "When Ctl-] + a character is pressed. go to that character."
          # Also named 'character-search'
          character_search(event.current_buffer, event.data, event.arg)
  
      @handle("escape", "c-]", Keys.Any)
      def _goto_char_backwards(event: E) -> None:
          "Like Ctl-], but backwards."
          # Also named 'character-search-backward'
          character_search(event.current_buffer, event.data, -event.arg)
  
      @handle("escape", "a")
      def _prev_sentence(event: E) -> None:
          "Previous sentence."
          # TODO:
  
      @handle("escape", "e")
      def _end_of_sentence(event: E) -> None:
          "Move to end of sentence."
          # TODO:
  
      @handle("escape", "t", filter=insert_mode)
      def _swap_characters(event: E) -> None:
          """
          Swap the last two words before the cursor.
          """
          # TODO
  
      @handle("escape", "*", filter=insert_mode)
      def _insert_all_completions(event: E) -> None:
          """
          `meta-*`: Insert all possible completions of the preceding text.
          """
          buff = event.current_buffer
  
          # List all completions.
          complete_event = CompleteEvent(
              text_inserted=False, completion_requested=True
          )
          completions = list(
              buff.completer.get_completions(
                  buff.document, complete_event
              )
          )
  
          # Insert them.
          text_to_insert = " ".join(c.text for c in completions)
          buff.insert_text(text_to_insert)
  
      @handle("c-x", "c-x")
      def _toggle_start_end(event: E) -> None:
          """
          Move cursor back and forth between the start and end of the current
          line.
          """
          buffer = event.current_buffer
  
          if buffer.document.is_cursor_at_the_end_of_line:
              buffer.cursor_position += (
                  buffer.document.get_start_of_line_position(
                      after_whitespace=False
                  )
              )
          else:
              buffer.cursor_position += (
                  buffer.document.get_end_of_line_position()
              )
  
      @handle("c-@")  # Control-space or Control-@
      def _start_selection(event: E) -> None:
          """
          Start of the selection (if the current buffer is not empty).
          """
          # Take the current cursor position as the start of this selection.
          buff = event.current_buffer
          if buff.text:
              buff.start_selection(
                  selection_type=SelectionType.CHARACTERS
              )
  
      @handle("c-g", filter=~has_selection)
      def _cancel(event: E) -> None:
          """
          Control + G: Cancel completion menu and validation state.
          """
          event.current_buffer.complete_state = None
          event.current_buffer.validation_error = None
  
      @handle("c-g", filter=has_selection)
      def _cancel_selection(event: E) -> None:
          """
          Cancel selection.
          """
          event.current_buffer.exit_selection()
  
      @handle("c-w", filter=has_selection)
      @handle("c-x", "r", "k", filter=has_selection)
      def _cut(event: E) -> None:
          """
          Cut selected text.
          """
          data = event.current_buffer.cut_selection()
          event.app.clipboard.set_data(data)
  
      @handle("escape", "w", filter=has_selection)
      def _copy(event: E) -> None:
          """
          Copy selected text.
          """
          data = event.current_buffer.copy_selection()
          event.app.clipboard.set_data(data)
  
      @handle("escape", "left")
      def _start_of_word(event: E) -> None:
          """
          Cursor to start of previous word.
          """
          buffer = event.current_buffer
          buffer.cursor_position += (
              buffer.document.find_previous_word_beginning(
                  count=event.arg
              )
              or 0
          )
  
      @handle("escape", "right")
      def _start_next_word(event: E) -> None:
          """
          Cursor to start of next word.
          """
          buffer = event.current_buffer
          buffer.cursor_position += (
              buffer.document.find_next_word_beginning(count=event.arg)
              or buffer.document.get_end_of_document_position()
          )
  
      @handle("escape", "/", filter=insert_mode)
      def _complete(event: E) -> None:
          """
          M-/: Complete.
          """
          b = event.current_buffer
          if b.complete_state:
              b.complete_next()
          else:
              b.start_completion(select_first=True)
  
      @handle("c-c", ">", filter=has_selection)
      def _indent(event: E) -> None:
          """
          Indent selected text.
          """
          buffer = event.current_buffer
  
          buffer.cursor_position += (
              buffer.document.get_start_of_line_position(
                  after_whitespace=True
              )
          )
  
          from_, to = buffer.document.selection_range()
          from_, _ = buffer.document.translate_index_to_position(from_)
          to, _ = buffer.document.translate_index_to_position(to)
  
          indent(buffer, from_, to + 1, count=event.arg)
  
      @handle("c-c", "<", filter=has_selection)
      def _unindent(event: E) -> None:
          """
          Unindent selected text.
          """
          buffer = event.current_buffer
  
          from_, to = buffer.document.selection_range()
          from_, _ = buffer.document.translate_index_to_position(from_)
          to, _ = buffer.document.translate_index_to_position(to)
  
          unindent(buffer, from_, to + 1, count=event.arg)
  
      return ConditionalKeyBindings(key_bindings, emacs_mode)
  
file_path: catboost/contrib/python/prompt-toolkit/py3/prompt_toolkit/key_binding/bindings/emacs.py
imports: from __future__ import annotations
  from prompt_toolkit.application.current import get_app
  from prompt_toolkit.buffer import Buffer, indent, unindent
  from prompt_toolkit.completion import CompleteEvent
  from prompt_toolkit.filters import Condition, emacs_insert_mode, emacs_mode, has_arg, has_selection, in_paste_mode, is_multiline, is_read_only, shift_selection_mode, vi_search_direction_reversed
  from prompt_toolkit.key_binding.key_bindings import Binding
  from prompt_toolkit.key_binding.key_processor import KeyPressEvent
  from prompt_toolkit.keys import Keys
  from prompt_toolkit.selection import SelectionType
  from ..key_bindings import ConditionalKeyBindings, KeyBindings, KeyBindingsBase
  from .named_commands import get_by_name
label_desc: Use image node_id 1 for calling a global function with example usage: load_emacs_bindings() and returns: ConditionalKeyBindings, get_app