def __init__(self, id1, id2=None, filter=None):
self.__id = link_ids(id1, id2)
self.__filter = filter
def __init__(self, id1, metadata, id2=None):
self.__id = link_ids(id1, id2)
self.__metadata = metadata
def __init__(self, id1, metadata, id2=None, lifetime=None):
self.__id = link_ids(id1, id2)
self.__metadata = metadata
self.__lifetime = lifetime
