How to use the @eth-optimism/contracts.getContractFactory function in @eth-optimism/contracts

getExtraData: async (event, l1RpcProvider) => {
    const l1Transaction = await event.getTransaction()
    const eventBlock = await event.getBlock()

    // TODO: We need to update our events so that we actually have enough information to parse this
    // batch without having to pull out this extra event. For the meantime, we need to find this
    // "TransactonBatchAppended" event to get the rest of the data.
    const OVM_CanonicalTransactionChain = getContractFactory(
      'OVM_CanonicalTransactionChain'
    )
      .attach(event.address)
      .connect(l1RpcProvider)

    const batchSubmissionEvent = (
      await OVM_CanonicalTransactionChain.queryFilter(
        OVM_CanonicalTransactionChain.filters.TransactionBatchAppended(),
        eventBlock.number,
        eventBlock.number
      )
    ).find((foundEvent: ethers.Event) => {
      // We might have more than one event in this block, so we specifically want to find a
      // "TransactonBatchAppended" event emitted immediately before the event in question.
      return (
        foundEvent.transactionHash === event.transactionHash &&

parseEvent: (event, extraData) => {
    const stateRoots = getContractFactory(
      'OVM_StateCommitmentChain'
    ).interface.decodeFunctionData(
      'appendStateBatch',
      extraData.l1TransactionData
    )[0]

    const stateRootEntries: StateRootEntry[] = []
    for (let i = 0; i < stateRoots.length; i++) {
      stateRootEntries.push({
        index: event.args._prevTotalElements.add(BigNumber.from(i)).toNumber(),
        batchIndex: event.args._batchIndex.toNumber(),
        value: stateRoots[i],
        confirmed: true,
      })
    }