How to use the @polkadot/extrinsics/codec/encode/prefixes.publicKey function in @polkadot/extrinsics

export default function signMessage (publicKey: Uint8Array, nonce: BN | number, value: Uint8Array, apiSupport: EncodingVersions): Signed {
  const message = encodeCall(publicKey, nonce, value, apiSupport);
  const signature = keyring.getPair(publicKey).sign(message);
  const data = u8aConcat(
    prefixes.publicKey,
    message,
    signature
  );

  console.log(`signMessage (${apiSupport}) :   message :: ${u8aToHex(message)}`);
  console.log(`signMessage (${apiSupport}) : signature :: ${u8aToHex(signature)}`);
  console.log(`signMessage (${apiSupport}) :      data :: ${u8aToHex(data)}`);

  return {
    data: u8aConcat(
      bnToU8a(data.length, 32, true),
      data
    ),
    message,
    signature
  };

export default function encodeType (type: Param$Type, value: any, version: EncodingVersions): Uint8Array {
  try {
    switch (type) {
      case 'AccountId':
        return u8aConcat(
          version === 'poc-1'
            ? addrPrefixes.none
            : addrPrefixes.publicKey,
          addressDecode(value)
        );

      case 'Balance':
        return bnToU8a(value, sizes.Balance.get(version) || defaultSizes.Balance, true);

      case 'BlockNumber':
      case 'Gas':
      case 'SessionKey':
      case 'u64':
        return bnToU8a(value, 64, true);

      case 'bool':
        return bnToU8a(value ? 1 : 0, 8, true);

      case 'Bytes':

export default function encodeType (type: Param$Type, value: any, version: EncodingVersions): Uint8Array {
  try {
    switch (type) {
      case 'AccountId':
        return u8aConcat(
          version === 'poc-1'
            ? addrPrefixes.none
            : addrPrefixes.publicKey,
          addressDecode(value)
        );

      case 'Balance':
        return bnToU8a(value, sizes.Balance.get(version) || defaultSizes.Balance, true);

      case 'BlockNumber':
      case 'Gas':
      case 'SessionKey':
      case 'u64':
        return bnToU8a(value, 64, true);

      case 'bool':
        return bnToU8a(value ? 1 : 0, 8, true);

      case 'Bytes':