rxjs/Subject.d.ts error : Class 'Subject' incorrectly extends base class 'Observable'

Question

I extracted sample template code from this tutorial and did below two steps to get started -

1. npm install // worked fine and created node_modules folder

Answer 1

Please change the following line of Subject.d.ts file:

lift(operator: Operator): Observable;

to:

lift(operator: Operator): Observable;

The return type should probably be Observable rather than Observable