def __init__(self, graph, subject):
        """Parameters:

        - graph:
            the graph containing the Seq

        - subject:
            the subject of a Seq. Note that the init does not
            check whether this is a Seq, this is done in whoever
            creates this instance!
        """

        _list = self._list = list()
        LI_INDEX = URIRef(str(RDF) + "_")
        for (p, o) in graph.predicate_objects(subject):
            if p.startswith(LI_INDEX):  # != RDF.Seq: #
                i = int(p.replace(LI_INDEX, ""))
                _list.append((i, o))

        # here is the trick: the predicates are _1, _2, _3, etc. Ie,
        # by sorting the keys (by integer) we have what we want!
        _list.sort()