Emitted when the user asks for it.
This is a [keybinding signal](class.SignalAction.html).
This is used to make the file chooser switch to the bookmark specified in the
bookmark_index parameter. For example, if you have
three bookmarks, you can pass 0, 1, 2 to this signal to switch to each of them, respectively.
The default binding for this signal is <kbd>Alt</kbd>-<kbd>1</kbd>, <kbd>Alt</kbd>-<kbd>2</kbd> , etc. until <kbd>Alt</kbd>-<kbd>0</kbd>. Note that in the default binding, that <kbd>Alt</kbd>-<kbd>1 </kbd> is actually defined to switch to the bookmark at index 0, and so on successively.
the number of the bookmark to switch to