How to use the slate-hotkeys.isMoveBackward function in slate-hotkeys

}

    if (Hotkeys.isExtendLineBackward(event)) {
      event.preventDefault()
      return editor.moveFocusToStartOfBlock()
    }

    if (Hotkeys.isExtendLineForward(event)) {
      event.preventDefault()
      return editor.moveFocusToEndOfBlock()
    }

    // COMPAT: If a void node is selected, or a zero-width text node adjacent to
    // an inline is selected, we need to handle these hotkeys manually because
    // browsers won't know what to do.
    if (Hotkeys.isMoveBackward(event)) {
      event.preventDefault()

      if (!selection.isCollapsed) {
        return editor.moveToStart()
      }

      return editor.moveBackward()
    }

    if (Hotkeys.isMoveForward(event)) {
      event.preventDefault()

      if (!selection.isCollapsed) {
        return editor.moveToEnd()
      }