'Find a sequence of node IDs in this path
@param sequence: sequence of node IDs (or path)
@return: position of the sequence (index+1), 0 if the path
is empty, -1 if the sequence wasn\'t found'

def find(self, sequence):

    path = S3MultiPath.Path(sequence)
    sequence = path.nodes
    nodes = self.nodes
    if (not sequence):
        return (-1)
    if (not nodes):
        return 0
    (head, tail) = (sequence[0], sequence[1:])
    pos = 0
    l = len(tail)
    index = nodes.index
    while (head in nodes[pos:]):
        pos = (index(head, pos) + 1)
        if ((not tail) or (nodes[pos:(pos + l)] == tail)):
            return pos
    return (-1)
