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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_b2aset(a2bset):
 """Given gene2gos, return go2genes. Given go2genes, return gene2gos."""

    b2aset = {}
    for a_item, bset in a2bset.items():
        for b_item in bset:
            if b_item in b2aset:
                b2aset[b_item].add(a_item)
            else:
                b2aset[b_item] = set([a_item])
    return b2aset