Model ancestry is used for comparison purposes when parallel development requires merging two sets of changes into a single final version of the model.

当并行开发需要将两个系列的变更合并为模型的单个最终版本时，就需要模型起始以进行比较了。

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Running in parallel with the trials of love is an account of the earliest vibrators, as developed for therapeutic purposes by our hero, the irony being that, without realizing it, he is, like Charlotte, in the business of female liberation.

NEWYORKER: Hysteria