set_callback

Set the callback used to filter the objects in the underlying collection.

The callback should return true if an object should appear in the filtered collection.

If a null callback is set, then all underlynig objects will appear in the filtered collection.

This will refilter the collection.

Parameters:

this	a filter collection
callback	function to call for each object
destroy_func	called for user_data when it is no longer needed
user_data	data to pass to the callback