We have to modify interface?

I cant understand if I have to write any code to the interface file PortfolioManager.java??
Please help @Crio-Admin, @Vinod_Crio_TA, @amanagar, @anand-crio.

No.
If you modify the interface, the tests will fail

@anand-crio Sir, that means we dont need to write any code PortfolioManager.java . Am I right?

Yes, you are doing the right thing by not doing anything in PortfolioManager.java