set_initial_file
Description:
Sets the file that will be initially selected in the file chooser dialog.
This function is a shortcut for calling both [method@Gtk.FileDialog.set_initial_folder] and [method@Gtk.FileDialog.set_initial_name] with the 
      directory and name of file, respectively.
Parameters:
| this | 
           a file dialog  | 
      
| file | 
           a file  |