Retrieves the text of the menu label for the page containing @child.
the child widget of a page of the notebook.
the text of the tab label, or %NULL if the widget does not have a menu label other than the default menu label, or the menu label widget is not a #GtkLabel. The string is owned by the widget and must not be freed.
See Implementation
Retrieves the text of the menu label for the page containing @child.