def map_node(s: Node, sk_s: URIRef, gin: Graph, gout: Graph) -> None:
    """
    Transform the BNode whose subject is s into its equivalent, replacing s with its 'skolemized' equivalent
    :param s: Actual subject
    :param sk_s: Equivalent URI of subject in output graph
    :param gin: Input graph
    :param gout: Output graph
    """
    for p, o in gin.predicate_objects(s):
        if not isinstance(o, BNode):
            gout.add((sk_s, p, o))
        else:
            sk_o = subj_pred_idx_to_uri(sk_s, p, gin.value(o, FHIR.index))
            gout.add((sk_s, p, sk_o))
            map_node(o, sk_o, gin, gout)