If we have a type which is a wrapped type like Promise, how we can get the type which is inside the wrapped type?

For example: if we have Promise<PromiseType> how to get PromiseType?

type PromiseType = Promise<string>

type Result = MyAwaited<PromiseType> // string

Please pay your attention that this type should unwrap nested promises:

type NestedPromiseType = Promise<Promise<Promise<string>>>;

type Result = MyAwaited<NestedPromiseType> // string

Note: In this challenge we also should take into account that type should be extracted not only from Promise type, but also from types that implement PromiseLike interface defined in lib.es5.d.ts.

// Test case:
MyAwaited<{ 
  then: (onfulfilled: (arg: number) => any) => any 
}> // expected number