How to use the ripple-keypairs.generateSeed function in ripple-keypairs

createAddressPrivatekey() {
        try {
          const t0 = performance.now();
          const seed = bip39.mnemonicToSeed(this.mnemonic); // creates seed buffer

          console.log('mnemonic: ' + this.mnemonic);

          var entropy = new Buffer(seed, 'hex');
          console.log("entropy", entropy);
          var secret = keypairs.generateSeed({entropy: entropy});
          var keypair = keypairs.deriveKeypair(secret);
          var publicKey = keypair.publicKey;
          var address = keypairs.deriveAddress(publicKey);
          var privateKey = keypair.privateKey;

          this.address = address;
          this.privateKey = privateKey;
          this.publicKey = publicKey;
          this.secret = secret;

          const t1 = performance.now();
          console.log(`Call to createAddressPrivatekey for each Ripple (${address}) took ${t1 - t0} milliseconds.`);
        } catch (e) {
          console.error(e);
        }
    }

'use strict'
const chalk = require('chalk')
const RippleKeypairs = require('ripple-keypairs')
const config = require('./config.json')

console.log(chalk.green('-----------------------------------------------'))
console.log(chalk.green('Ripple Wallet'), chalk.yellow('Generate Wallet'))
console.log(chalk.green('-----------------------------------------------'), '\n')

const seed = RippleKeypairs.generateSeed()
const keypair = RippleKeypairs.deriveKeypair(seed)
const address = RippleKeypairs.deriveAddress(keypair.publicKey)

console.log('  Public address:', chalk.yellow(address))
console.log('  Wallet secret:', chalk.yellow(seed), '\n')

console.log(chalk.red('  Print this wallet and make sure to store it somewhere safe!'), '\n')
console.log(`  Note: You need to put at least ${config.baseReserve} ${config.currency} on this key for it to be an active account\n`)

generate: function(s){
      seed = rippleKeypairs.generateSeed({entropy: s})
      keypair = rippleKeypairs.deriveKeypair(seed)
      return  rippleKeypairs.deriveAddress(keypair.publicKey)
    }
  },

function generateAddressAPI(options: GenerateAddressOptions): GeneratedAddress {
  validate.generateAddress({options})
  try {
    const secret = keypairs.generateSeed(options)
    const keypair = keypairs.deriveKeypair(secret)
    const classicAddress = keypairs.deriveAddress(keypair.publicKey)
    const returnValue: any = {
      xAddress: classicAddressToXAddress(
        classicAddress,
        false,
        options && options.test
      ),
      secret
    }
    if (options.includeClassicAddress) {
      returnValue.classicAddress = classicAddress
      returnValue.address = classicAddress
    }
    return returnValue
  } catch (error) {