How to use the knex.Promise.coroutine function in knex

for (i = 0; i < modelClasses.length; ++i) {
      if (!isSubclassOf(modelClasses[i], Model)) {
        return Promise.reject(new Error('objection.transaction: all but the last argument should be Model subclasses'));
      }
    }

    let knex = _.first(modelClasses).knex();
    for (i = 0; i < modelClasses.length; ++i) {
      if (modelClasses[i].knex() !== knex) {
        return Promise.reject(new Error('objection.transaction: all Model subclasses must be bound to the same database'));
      }
    }

    // If the function is a generator, wrap it using Promise.coroutine.
    if (isGenerator(callback)) {
      callback = Promise.coroutine(callback);
    }

    return knex.transaction(trx => {
      let args = new Array(modelClasses.length + 1);

      for (let i = 0; i < modelClasses.length; ++i) {
        args[i] = modelClasses[i].bindTransaction(trx);
      }

      args[args.length - 1] = trx;

      return Promise.try(() => {
        return callback.apply(trx, args);
      });
    });
  }

export default function transaction() {
  // There must be at least one model class and the callback.
  if (arguments.length < 2) {
    return Promise.reject(new Error('objection.transaction: provide at least one Model class to bind to the transaction or a knex instance'));
  }

  if (!isSubclassOf(arguments[0], Model) && _.isFunction(arguments[0].transaction)) {
    let args = _.toArray(arguments);
    let knex = _.first(args);
    args = args.slice(1);

    // If the function is a generator, wrap it using Promise.coroutine.
    if (isGenerator(args[0])) {
      args[0] = Promise.coroutine(args[0]);
    }

    return knex.transaction.apply(knex, args);
  } else {
    // The last argument should be the callback and all other Model subclasses.
    let callback = _.last(arguments);
    let modelClasses = _.take(arguments, arguments.length - 1);
    let i;

    for (i = 0; i < modelClasses.length; ++i) {
      if (!isSubclassOf(modelClasses[i], Model)) {
        return Promise.reject(new Error('objection.transaction: all but the last argument should be Model subclasses'));
      }
    }

    let knex = _.first(modelClasses).knex();