def find_ref_chain(obj, predicate, max_depth=20, extra_ignore=()):
 return _find_chain(obj, predicate, gc.get_referents, max_depth=max_depth, extra_ignore=extra_ignore)[::(-1)]

def find_ref_chain ( obj , predicate , max_depth = 20 , extra_ignore = ( ) ) : return _find_chain ( obj , predicate , gc . get_referents , max_depth = max_depth , extra_ignore = extra_ignore ) [ : : ( - 1 ) ]
find a shortest chain of references leading from obj .