How to use the tns-core-modules/utils/types.isString function in tns-core-modules

export function prompt(arg: any): Promise {
    let options: PromptOptions & MDCAlertControlerOptions;

    const defaultOptions = {
        title: PROMPT,
        okButtonText: OK,
        cancelButtonText: CANCEL,
        inputType: inputType.text
    };

    if (arguments.length === 1) {
        if (isString(arg)) {
            options = defaultOptions;
            options.message = arg;
        } else {
            options = Object.assign(defaultOptions, arg);
        }
    } else if (arguments.length === 2) {
        if (isString(arguments[0]) && isString(arguments[1])) {
            options = defaultOptions;
            options.message = arguments[0];
            options.defaultText = arguments[1];
        }
    }

    return new Promise((resolve, reject) => {
        try {
            // let textField: MDCTextField;

return new Promise(function (resolve, reject) {
            try {
                let i = void 0;
                let alertController = UIAlertController.alertControllerWithTitleMessagePreferredStyle(options && options.title ? options.title : null, options && options.message ? options.message : null, 0);
                if (options.actions) {
                    for (i = 0; i < options.actions.length; i++) {
                        let action = options.actions[i];
                        if (Types.isString(action)) {
                            alertController.addAction(UIAlertAction.actionWithTitleStyleHandler(action, 0, arg => {
                                resolve({
                                    id: options.actions.indexOf(arg.title),
                                    title: arg.title
                                });
                            }));
                        } else if (Types.isString(action.title)) {
                            alertController.addAction(UIAlertAction.actionWithTitleStyleHandler(action.title, 0, arg => {
                                resolve(Object.assign({
                                    id: options.actions.find(actionItem => actionItem.title === arg.title).id || options.actions.indexOf(options.actions.find(actionItem => actionItem.title === arg.title))
                                }, options.actions.find(actionItem => actionItem.title === arg.title)));
                            }));
                        }
                    }
                }
                if (Types.isString(options.cancelButtonText)) {
                    alertController.addAction(UIAlertAction.actionWithTitleStyleHandler(options.cancelButtonText, 1, arg => {
                        resolve(false);
                    }));
                }
                showUIAlertController(alertController);
            }
            catch (error) {

export function action(): Promise {
    let options: ActionOptions;

    const defaultOptions = { title: null, cancelButtonText: CANCEL };

    if (arguments.length === 1) {
        if (isString(arguments[0])) {
            options = defaultOptions;
            options.message = arguments[0];
        } else {
            options = arguments[0];
        }
    } else if (arguments.length === 2) {
        if (isString(arguments[0]) && isString(arguments[1])) {
            options = defaultOptions;
            options.message = arguments[0];
            options.cancelButtonText = arguments[1];
        }
    } else if (arguments.length === 3) {
        if (isString(arguments[0]) && isString(arguments[1]) && isDefined(arguments[2])) {
            options = defaultOptions;
            options.message = arguments[0];
            options.cancelButtonText = arguments[1];
            options.actions = arguments[2];
        }
    }

    return new Promise((resolve, reject) => {
        try {
            let i: number;

export function boolParse(value: any) {
  if (types.isString(value)) {
    switch (value.toLowerCase()) {
      case 'yes':
        return true;
      default:
        return false;
    }
  } else if (types.isBoolean(value)) {
    return value;
  }
  return false;
}
export const srcProperty = new Property({

const alertController = createAlertController(options, resolve);

            if (options.actions) {
                for (i = 0; i < options.actions.length; i++) {
                    action = options.actions[i];
                    if (isString(action)) {
                        alertController.addAction(
                            MDCAlertAction.actionWithTitleEmphasisHandler(action, MDCActionEmphasis.Low, (arg: MDCAlertAction) => {
                                resolve(arg.title);
                            })
                        );
                    }
                }
            }

            if (isString(options.cancelButtonText)) {
                alertController.addAction(
                    MDCAlertAction.actionWithTitleEmphasisHandler(options.cancelButtonText, MDCActionEmphasis.Low, (arg: MDCAlertAction) => {
                        resolve(arg.title);
                    })
                );
            }

            showUIAlertController(alertController);
        } catch (ex) {
            reject(ex);
        }
    });
}

[common.errorHolderProperty.setNative](errorHolder: any) {
        const holder = ImageCacheIt.getImage(errorHolder);
        if (this.nativeView) {
            if (types.isString(errorHolder) && errorHolder.startsWith('res://')) {
                this.nativeView.setErrorHolder(errorHolder);
            } else {
                this.nativeView.setErrorHolder(holder);
            }
        }
    }

function addButtonsToAlertController(alertController: MDCAlertController, options: ConfirmOptions, callback?: Function, validation?: Function): void {
    if (!options) {
        return;
    }

    if (isString(options.cancelButtonText)) {
        alertController.addAction(
            MDCAlertAction.actionWithTitleEmphasisHandler(options.cancelButtonText, MDCActionEmphasis.Low, () => {
                raiseCallback(callback, false);
            })
        );
    }

    if (isString(options.neutralButtonText)) {
        alertController.addAction(
            MDCAlertAction.actionWithTitleEmphasisHandler(options.neutralButtonText, MDCActionEmphasis.Low, () => {
                raiseCallback(callback, undefined);
            })
        );
    }

    if (isString(options.okButtonText)) {
        alertController.addAction(
            MDCAlertAction.actionWithTitleEmphasisHandler(options.okButtonText, MDCActionEmphasis.Low, () => {
                if (validation && !validation(options)) {
                    return;
                }
                raiseCallback(callback, true);
            })
        );

alertController.addAction(
            MDCAlertAction.actionWithTitleEmphasisHandler(options.cancelButtonText, MDCActionEmphasis.Low, () => {
                raiseCallback(callback, false);
            })
        );
    }

    if (isString(options.neutralButtonText)) {
        alertController.addAction(
            MDCAlertAction.actionWithTitleEmphasisHandler(options.neutralButtonText, MDCActionEmphasis.Low, () => {
                raiseCallback(callback, undefined);
            })
        );
    }

    if (isString(options.okButtonText)) {
        alertController.addAction(
            MDCAlertAction.actionWithTitleEmphasisHandler(options.okButtonText, MDCActionEmphasis.Low, () => {
                raiseCallback(callback, true);
            })
        );
    }
}

export function login(arg: any): Promise {
    let options: LoginOptions & MDCAlertControlerOptions;

    const defaultOptions = {
        title: LOGIN,
        okButtonText: OK,
        cancelButtonText: CANCEL
    };

    if (arguments.length === 1) {
        if (isString(arguments[0])) {
            options = defaultOptions;
            options.message = arguments[0];
        } else {
            options = Object.assign(defaultOptions, arguments[0]);
        }
    } else if (arguments.length === 2) {
        if (isString(arguments[0]) && isString(arguments[1])) {
            options = defaultOptions;
            options.message = arguments[0];
            options.userName = arguments[1];
        }
    } else if (arguments.length === 3) {
        if (isString(arguments[0]) && isString(arguments[1]) && isString(arguments[2])) {
            options = defaultOptions;
            options.message = arguments[0];
            options.userName = arguments[1];

private static getResourceId(res: string = '') {
        if (types.isString(res) && res.startsWith('res://')) {
            return java.lang.Integer.valueOf(utils.ad.resources.getDrawableId(res.replace('res://', '')));
        }
        return java.lang.Integer.valueOf(0);
    }