title: How can I set app title after loading UI using Gtk.Builder() in python?
body: <p>I'm trying to set the app title using set_wmclass but I'm getting a Gtk-WARNING and finally app name is not set.</p>
  
  <blockquote>
    <p>Gtk-WARNING **: gtk_window_set_wmclass: shouldn't set wmclass after
    window is realized!</p>
  </blockquote>
  
  <p>I'm using Gtk.Builder() to load the window UI from a glade file like this...</p>
  
  <pre><code>ui_builder = Gtk.Builder()
  ui_builder.add_from_file('window.ui')
  window = ui_builder.get_object('window1')
  self.__window.set_wmclass("Hello World", "Hello World")
  </code></pre>