set_model
Description:
Sets the model for a `GtkEntryCompletion`.
Note: 
      
        
    
    GtkEntryCompletion will be removed in GTK 5.
If this already has a model set, it will remove it before setting the new model. If model is null, then it will unset the model.
Parameters:
| this | 
           a `GtkEntryCompletion`  | 
      
| model | 
           the `GtkTreeModel`  |