How to use the braintree-web/venmo.create function in braintree-web

VenmoView.prototype.initialize = function () {
  var self = this;
  var venmoConfiguration = assign({}, self.model.merchantConfiguration.venmo, {client: this.client});

  self.model.asyncDependencyStarting();

  return btVenmo.create(venmoConfiguration).then(function (venmoInstance) {
    self.venmoInstance = venmoInstance;

    if (!self.venmoInstance.hasTokenizationResult()) {
      return Promise.resolve();
    }

    return self.venmoInstance.tokenize().then(function (payload) {
      self.model.reportAppSwitchPayload(payload);
    }).catch(function (err) {
      if (self._isIgnorableError(err)) {
        return;
      }
      self.model.reportAppSwitchError(paymentOptionIDs.venmo, err);
    });
  }).then(function () {
    var button = self.getElementById('venmo-button');