def METHOD_NAME(spec, start_slot, block_lengths, custody_secret, slashable=True):
    shard_transition = get_sample_shard_transition(spec, start_slot, block_lengths)
    slashable_test_vector = get_custody_slashable_test_vector(spec, custody_secret,
                                                              block_lengths[0], slashable=slashable)
    block_data = ByteList[spec.MAX_SHARD_BLOCK_SIZE](slashable_test_vector)
    shard_transition.shard_data_roots[0] = spec.hash_tree_root(block_data)
    return shard_transition, slashable_test_vector