Insert a page into notebook at the given position.
the gtk.Widget to use as the contents of the page
the gtk.Widget to be used as the label for the page, or NULL to use the default label, “page N”
the index (starting at 0) at which to insert the page, or -1 to append the page after all other pages
the index (starting from 0) of the inserted page in the notebook, or -1 if function fails