How to use the @polkadot/extrinsics/codec/encode/uncheckedLength.default function in @polkadot/extrinsics

async function transfer (keyRingFrom, addressTo, amount) {
  const nextAccountIndex = await getAccountIndex(keyRingFrom.address());

  // encode the call for signing
  const encoded = encodeExtrinsic(
    keyRingFrom,
    nextAccountIndex,
    extrinsics.staking.public.transfer,
    [addressTo, amount]
  );

  await api.author.submitExtrinsic(encoded)
    .catch(e => console.log);
}