'how to print out a forward index in whoosh?

I am looking on a way to display the forward index using the whoosh library in python. Suppose we have an index and we want to display like that:

Doc Postings
1   [(text=apple, freq=2)]
2   [(text=apple, freq=5), (text='bear', freq=7)]
3   [(text=apple, freq=1)]

python whoosh

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