Cannot set true value for I18nManager.allowRTL

I would like to enable RTL on my iOS project using EXPO.

Then I tried to enable like

I18nManager.allowRTL(true); 

It cannot be set to true.I checked the value by using the following code

console.log('Value is: '+I18nManager.isRTL);//This always retuns FALSE

Please help me how to solve this issue