How does qDebug() print a line break?

[Cruz]

You now how when you

qDebug() << 1 << 2 << 3;

qDebug() << 1 << 2 << 3;

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it neatly prints a line break after the 3? How does the << operator know which one is the last item in the chain?
I would like to borrow (steal, really) this feature for a custom file logger I wrote where I would like to chain the
<< operator and it should put a line break after the last item.