code: def load_emacs_bindings():
      """
      Some e-macs extensions.
      """
      # Overview of Readline emacs commands:
      # http://www.catonmat.net/download/readline-emacs-editing-mode-cheat-sheet.pdf
      registry = ConditionalRegistry(Registry(), EmacsMode())
      handle = registry.add_binding
  
      insert_mode = EmacsInsertMode()
      has_selection = HasSelection()
  
      @handle(Keys.Escape)
      def _(event):
          """
          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(Keys.ControlA)(get_by_name("beginning-of-line"))
      handle(Keys.ControlB)(get_by_name("backward-char"))
      handle(Keys.ControlDelete, filter=insert_mode)(
          get_by_name("kill-word")
      )
      handle(Keys.ControlE)(get_by_name("end-of-line"))
      handle(Keys.ControlF)(get_by_name("forward-char"))
      handle(Keys.ControlLeft)(get_by_name("backward-word"))
      handle(Keys.ControlRight)(get_by_name("forward-word"))
      handle(Keys.ControlX, "r", "y", filter=insert_mode)(
          get_by_name("yank")
      )
      handle(Keys.ControlY, filter=insert_mode)(get_by_name("yank"))
      handle(Keys.Escape, "b")(get_by_name("backward-word"))
      handle(Keys.Escape, "c", filter=insert_mode)(
          get_by_name("capitalize-word")
      )
      handle(Keys.Escape, "d", filter=insert_mode)(
          get_by_name("kill-word")
      )
      handle(Keys.Escape, "f")(get_by_name("forward-word"))
      handle(Keys.Escape, "l", filter=insert_mode)(
          get_by_name("downcase-word")
      )
      handle(Keys.Escape, "u", filter=insert_mode)(
          get_by_name("uppercase-word")
      )
      handle(Keys.Escape, "y", filter=insert_mode)(
          get_by_name("yank-pop")
      )
      handle(Keys.Escape, Keys.ControlH, filter=insert_mode)(
          get_by_name("backward-kill-word")
      )
      handle(Keys.Escape, Keys.Backspace, filter=insert_mode)(
          get_by_name("backward-kill-word")
      )
      handle(Keys.Escape, "\\", filter=insert_mode)(
          get_by_name("delete-horizontal-space")
      )
  
      handle(
          Keys.ControlUnderscore,
          save_before=(lambda e: False),
          filter=insert_mode,
      )(get_by_name("undo"))
  
      handle(
          Keys.ControlX,
          Keys.ControlU,
          save_before=(lambda e: False),
          filter=insert_mode,
      )(get_by_name("undo"))
  
      handle(Keys.Escape, "<", filter=~has_selection)(
          get_by_name("beginning-of-history")
      )
      handle(Keys.Escape, ">", filter=~has_selection)(
          get_by_name("end-of-history")
      )
  
      handle(Keys.Escape, ".", filter=insert_mode)(
          get_by_name("yank-last-arg")
      )
      handle(Keys.Escape, "_", filter=insert_mode)(
          get_by_name("yank-last-arg")
      )
      handle(Keys.Escape, Keys.ControlY, filter=insert_mode)(
          get_by_name("yank-nth-arg")
      )
      handle(Keys.Escape, "#", filter=insert_mode)(
          get_by_name("insert-comment")
      )
      handle(Keys.ControlO)(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(Keys.ControlQ, filter=~has_selection)(
          get_by_name("quoted-insert")
      )
  
      handle(Keys.ControlX, "(")(get_by_name("start-kbd-macro"))
      handle(Keys.ControlX, ")")(get_by_name("end-kbd-macro"))
      handle(Keys.ControlX, "e")(get_by_name("call-last-kbd-macro"))
  
      @handle(Keys.ControlN)
      def _(event):
          "Next line."
          event.current_buffer.auto_down()
  
      @handle(Keys.ControlP)
      def _(event):
          "Previous line."
          event.current_buffer.auto_up(count=event.arg)
  
      def handle_digit(c):
          """
          Handle input of arguments.
          The first number needs to be preceeded by escape.
          """
  
          @handle(c, filter=HasArg())
          @handle(Keys.Escape, c)
          def _(event):
              event.append_to_arg_count(c)
  
      for c in "0123456789":
          handle_digit(c)
  
      @handle(Keys.Escape, "-", filter=~HasArg())
      def _(event):
          """ """
          if event._arg is None:
              event.append_to_arg_count("-")
  
      @handle(
          "-",
          filter=Condition(lambda cli: cli.input_processor.arg == "-"),
      )
      def _(event):
          """
          When '-' is typed again, after exactly '-' has been given as an
          argument, ignore this.
          """
          event.cli.input_processor.arg = "-"
  
      is_returnable = Condition(
          lambda cli: cli.current_buffer.accept_action.is_returnable
      )
  
      # Meta + Newline: always accept input.
      handle(
          Keys.Escape, Keys.ControlJ, filter=insert_mode & is_returnable
      )(get_by_name("accept-line"))
  
      def character_search(buff, char, count):
          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(Keys.ControlSquareClose, Keys.Any)
      def _(event):
          "When Ctl-] + a character is pressed. go to that character."
          # Also named 'character-search'
          character_search(event.current_buffer, event.data, event.arg)
  
      @handle(Keys.Escape, Keys.ControlSquareClose, Keys.Any)
      def _(event):
          "Like Ctl-], but backwards."
          # Also named 'character-search-backward'
          character_search(event.current_buffer, event.data, -event.arg)
  
      @handle(Keys.Escape, "a")
      def _(event):
          "Previous sentence."
          # TODO:
  
      @handle(Keys.Escape, "e")
      def _(event):
          "Move to end of sentence."
          # TODO:
  
      @handle(Keys.Escape, "t", filter=insert_mode)
      def _(event):
          """
          Swap the last two words before the cursor.
          """
          # TODO
  
      @handle(Keys.Escape, "*", filter=insert_mode)
      def _(event):
          """
          `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(Keys.ControlX, Keys.ControlX)
      def _(event):
          """
          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(Keys.ControlSpace)
      def _(event):
          """
          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(Keys.ControlG, filter=~has_selection)
      def _(event):
          """
          Control + G: Cancel completion menu and validation state.
          """
          event.current_buffer.complete_state = None
          event.current_buffer.validation_error = None
  
      @handle(Keys.ControlG, filter=has_selection)
      def _(event):
          """
          Cancel selection.
          """
          event.current_buffer.exit_selection()
  
      @handle(Keys.ControlW, filter=has_selection)
      @handle(Keys.ControlX, "r", "k", filter=has_selection)
      def _(event):
          """
          Cut selected text.
          """
          data = event.current_buffer.cut_selection()
          event.cli.clipboard.set_data(data)
  
      @handle(Keys.Escape, "w", filter=has_selection)
      def _(event):
          """
          Copy selected text.
          """
          data = event.current_buffer.copy_selection()
          event.cli.clipboard.set_data(data)
  
      @handle(Keys.Escape, Keys.Left)
      def _(event):
          """
          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(Keys.Escape, Keys.Right)
      def _(event):
          """
          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(Keys.Escape, "/", filter=insert_mode)
      def _(event):
          """
          M-/: Complete.
          """
          b = event.current_buffer
          if b.complete_state:
              b.complete_next()
          else:
              event.cli.start_completion(select_first=True)
  
      @handle(Keys.ControlC, ">", filter=has_selection)
      def _(event):
          """
          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(Keys.ControlC, "<", filter=has_selection)
      def _(event):
          """
          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 registry
  
file_path: catboost/contrib/python/prompt-toolkit/py2/prompt_toolkit/key_binding/bindings/emacs.py
imports: from __future__ import unicode_literals
  from prompt_toolkit.buffer import SelectionType, indent, unindent
  from prompt_toolkit.keys import Keys
  from prompt_toolkit.enums import IncrementalSearchDirection, SEARCH_BUFFER, SYSTEM_BUFFER
  from prompt_toolkit.filters import Condition, EmacsMode, HasSelection, EmacsInsertMode, HasFocus, HasArg
  from prompt_toolkit.completion import CompleteEvent
  from .scroll import scroll_page_up, scroll_page_down
  from .named_commands import get_by_name
  from ..registry import Registry, ConditionalRegistry
label_desc: Use image node_id 1 for calling a global function with example usage: load_emacs_bindings() and returns: registry