How to use the libsodium-wrappers-sumo.crypto_sign_detached function in libsodium-wrappers-sumo

TransactionHelper.prototype.signShielded = function (signatureHashFn) {
  // Empty output script
  var scriptCode = Buffer.alloc(0)
  var dataToBeSigned = signatureHashFn(NOT_AN_INPUT, scriptCode, SIGHASH_ALL)

  // Add the signature
  this.joinSplitSig = Buffer.from(sodium.crypto_sign_detached(dataToBeSigned, this._joinSplitPrivKey))

  // Sanity check
  sodium.crypto_sign_verify_detached(this.joinSplitSig, dataToBeSigned, this.joinSplitPubKey)
}

sign(message: Uint8Array | string): Uint8Array {
    return sodium.crypto_sign_detached(message, this.sec_edward);
  }

sign(message: Uint8Array): Uint8Array {
    return sodium.crypto_sign_detached(message, this.sec_edward);
  }

const sign = async (message, key) => {
    await sodiumsumo.ready;
    return sodiumsumo.crypto_sign_detached(message, key);
}

switch (sk && Buffer.byteLength(sk)) {
    case sodium.crypto_sign_SECRETKEYBYTES:
      isk = sk;
      break;
    case sodium.crypto_sign_SEEDBYTES:
      isk = sodium.crypto_sign_seed_keypair(sk).privateKey;
      break;
    default:
      isk = sodium.crypto_sign_keypair().privateKey;
      sk  = sodium.crypto_sign_ed25519_sk_to_seed(isk);
  }

  let signature;
  try {
    signature = sodium.crypto_sign_detached(payload, isk);
  } catch(ex) {
    return done(new Error('Libsodium error: ' + ex));
  }

  return done(null, convert({
    alg:       'ed25519',
    sk:        sk,
    payload:   payload,
    signature: signature
  }));
}