@staticmethod
def order(links, n):
    """
    Give a list of Links that each contain node n, flips any links so
    that n is always the first element of the link.
    """
    r = []
    for l in links:
        assert n in l
        if l._n[0] == n:
            r.append(l)
        else:
            r.append(l.flip())
    return r
