def recurse( record, index, stop_types=STOP_TYPES,already_seen=None, type_group=False ):
    """Depth first traversal of a tree, all children are yielded before parent
    
    record -- dictionary record to be recursed upon 
    index -- mapping 'address' ids to dictionary records 
    stop_types -- types which will *not* recurse 
    already_seen -- set storing already-visited nodes 
    
    yields the traversed nodes
    """
    if already_seen is None:
        already_seen = set()
    if record['address'] not in already_seen:
        already_seen.add(record['address'])
        if 'refs' in record:
            for child in children( record, index, stop_types=stop_types ):
                if child['address'] not in already_seen:
                    for descendant in recurse( 
                        child, index, stop_types, 
                        already_seen=already_seen, type_group=type_group,
                    ):
                        yield descendant
        yield record
Depth first traversal of a tree, all children are yielded before parent
    
    record -- dictionary record to be recursed upon 
    index -- mapping 'address' ids to dictionary records 
    stop_types -- types which will *not* recurse 
    already_seen -- set storing already-visited nodes 
    
    yields the traversed nodes