the GtkWidget to use as the contents of the page.
the GtkWidget to be used as the label for the page, or NULL to use the default label, 'page N'. [allow-none]
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
Insert a page into notebook at the given position.