How to use the exonum-client.Uint32 function in exonum-client

const buildMessage = (header, body, keyPair) => {
  const unsignedMessage = appendBuffer(new Uint8Array(header), body)

  // calculate payload and insert it into buffer
  Exonum.Uint32.serialize(unsignedMessage.length + SIGNATURE_LENGTH, unsignedMessage, PAYLOAD_SIZE_OFFSET)

  // calculate signature
  const signature = Exonum.sign(keyPair.secretKey, unsignedMessage)

  // append signature to the message
  return appendBuffer(unsignedMessage, Exonum.hexadecimalToUint8Array(signature))
}

const PROTOCOL_VERSION = 0
const SERVICE_ID = 42
const TX_TRANSFER_ID = 2
const TX_WALLET_ID = 1
const SIGNATURE_LENGTH = 64
const PAYLOAD_SIZE_OFFSET = 6
const PER_PAGE = 10
const MAX_VALUE = 2147483647

const MessageHead = Exonum.newType({
  fields: [
    { name: 'network_id', type: Exonum.Uint8 },
    { name: 'protocol_version', type: Exonum.Uint8 },
    { name: 'message_id', type: Exonum.Uint16 },
    { name: 'service_id', type: Exonum.Uint16 },
    { name: 'payload', type: Exonum.Uint32 }
  ]
})

function getWallet (publicKey) {
  return axios.get(`/api/cryptocurrency-demo-service/wallet/${publicKey}`)
    .then(response => response.data)
    .then(data => {
      return {
        wallet: data,
        transactions: []
      }
    })
}

function waitForAcceptance (publicKey, hash) {
  let attempt = ATTEMPTS