PangoAttrList and callback function, removes any elements
of list for which func returns TRUE and inserts them into
a new list.pangoAttrListFilter(object, func, data)objectfuncPangoAttrFilterFunc] callback function; returns TRUE if an attribute
should be filtered out.datafuncPangoAttrList] the new PangoAttrList or NULL if
no attributes of the given types were found.