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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 key_rollover(kb):
 """ A nifty function that lets you do a key rollover that encompasses creating a completely new set of keys. One new per every old one. With the same specifications as the old one. All the old ones are marked as inactive. :param kb: :return: """

    key_spec = []
    for key in kb.get():
        _spec = {'type': key.kty, 'use':[key.use]}
        if key.kty == 'EC':
            _spec['crv'] = key.crv

        key_spec.append(_spec)

    diff = {'del': kb.get()}
    _kb = build_key_bundle(key_spec)
    diff['add'] = _kb.keys()

    update_key_bundle(kb, diff)
    return kb