set:trailing returns the nodes in one node-set that come after the first node in the other node-set, in document order.
trailing 将返回一个节点集，其中的节点按照文档顺序要比另一个节点集中的第一个节点晚出现。
Three or four Francie's lovers now appeared, one after the other; she had made each promise to come early.
这时佛兰茜的情人陆续来了三四个；是她事先逼着每一个人应早到的。
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