code: def key_rollover(kb):
      
      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
docs: 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: