Jwt auth0节点jsonwebtoken中没有的选项是什么？

我在读书https://github.com/auth0/node-jsonwebtokenjwtsignpayload-secretorprivatekey-options-callback 文件

它说：

notBefore：以秒或描述时间跨度的字符串表示。 例：60，2天，10小时，7天。数值被解释为秒数。如果使用字符串，请确保提供时间单位天、小时等，否则默认情况下使用毫秒单位120等于120ms

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此选项用于什么？

您可以查看此文档

第4.1.5节。nbf不在索赔之前

The "nbf" (not before) claim identifies the time before which the JWT
   MUST NOT be accepted for processing.  The processing of the "nbf"
   claim requires that the current date/time MUST be after or equal to
   the not-before date/time listed in the "nbf" claim.  Implementers MAY
   provide for some small leeway, usually no more than a few minutes, to
   account for clock skew.  Its value MUST be a number containing a
   NumericDate value.  Use of this claim is OPTIONAL.