Query regarding the Gtk::Label::modify_font() function

["flideravi gmail com" <flideravi gmail com>]

hello all, 
I am new to gtkmm. I was trying out the video tutorials on "http://blog.spacefish.be" and in one of the videos he used Pango::FontDescription object to describe and font and then changed the font of a label using Gtk::Label::modify_font() function [label.modify_font(font), where, label is an object of Gtk::Label and font is an object of Pango::FontDescription], but in my code compiler produces error saying that no such function exist in the Gtk::Label class, however it runs perfectly fine in the tutorial. 
What might be the reason for this? Has the above mentioned function been deleted form the API?

fLiDe