Recall that the constructor takes the cache object as an optional argument.
回想一下，构造函数以可选参数的方式接受缓存对象。
The function has the syntax IRR (range of cash flows, [guess]), where guess is an optional argument.
函数的语法为IRR(现金流区域 [guess])这里的 guess是一个可选参数（预测值）.
The MetadataServlet works the same way but has an optional argument that the metadata service implementation can use as a hint to retrieve the metadata.
MetadataServlet也是这样工作，但是有一个可选的参数，可以被元数据服务实现做为提取元数据的一个提示。
You can add an optional argument, a variable that holds the return code from the external program, such as 0 for success, which provides a better mechanism for debugging.
您可以添加可选的参数，即保存从外部程序返回的代码的变量，比如表示成功的0，这为调试提供更好的机制。
The open-parenthesis is followed by an optional argument list.
开括号后面跟着一个可选的参数列表。
The open-parenthesis is followed by an optional argument list.
开括号后面跟着一个可选的参数列表。
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