title: In Gobject, how to override parent class's method belong to an interface?
body: <p>GObject class A implements interface IA,  B is a derived class of A.  How can B override A's method that is part of the interface IA?  </p>
  
  <p>Or, is this possible in GObject?</p>
  
  <p>I know how to override parent class methods, but when inheritance meets interface, things seems to be more complicated.</p>
  
  <p>Thanks a lot!</p>