The attributes set with this function will be applied and merged with
any other attributes previously effected by way of the
[property@Gtk.Label:use-underline] or [property@Gtk.Label:use-markup]
properties. While it is not recommended to mix markup strings with
manually set attributes, if you must; know that the attributes will
be applied to the label after the markup string is parsed.
Apply attributes to the label text.
The attributes set with this function will be applied and merged with any other attributes previously effected by way of the [property@Gtk.Label:use-underline] or [property@Gtk.Label:use-markup] properties. While it is not recommended to mix markup strings with manually set attributes, if you must; know that the attributes will be applied to the label after the markup string is parsed.