You can do the same thing for the Contract class, as shown in Listing 3.

您可以为contract类做相同的事情，如清单3所示。

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Perhaps a first-class Contract class should be created to represent the relationship between Book and Author better.

或许应该创建一个一级类Contract来更好地表示Book与Author之间的关系。

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Middle-class families contract with a puller to take a child to school and pick him up; the puller essentially becomes a family retainer.

中产阶级家庭与车夫签订合同，让他送孩子去学校以及接孩子放学。车夫实际上变成了一位家仆。

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Carnival's contract prohibits a class action suit, but Hickey said he's not sure whether it is legally enforceable.

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Middle class economies contract.

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He seamlessly switches from asbestos lawsuits, which involve individual plaintiffs who each signed a contract with their lawyer, and class actions where lawyers purport to act on behalf of thousands or millions of people who may not even know the case exists.

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