Sets a PangoAttrList; the attributes in the list are applied to the label text. <note><para>The attributes set with this function will be applied and merged with any other attributes previously effected by way of the GtkLabel:use-underline or GtkLabel: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.</para></note>