The function in Listing 20 returns a vector of vectors. This is because each document could generate zero to many map entries, and each map entry is represented as a vector.

清单 20 中的函数返回矢量的矢量，这是因为每个文档都可能生成零到多个映射条目，而每个映射条目都被表示为一个矢量。

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Many Map Zoom levels.

许多地图缩放等级。

youdao

That's the thankless job of Special Agent Gray Hill, who unfortunately fails to reunite many a map with its proper home, even after months of investigation.

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Though these wines are stylistically all over the map, many of the best Oregon Pinot Gris have settled happily into a niche somewhere between the full-bodied, powerful style of Alsace and the lighter wines of central Italy.

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How many people carry around the map of Alaska in their heads?

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