code: public final <R1 extends R> Invokable<T, R1> returning(Class<R1> returnType) {
      return returning(TypeToken.of(returnType));
    }
docs: Explicitly specifies the return type of this {@code Invokable}. For example:
  
  <pre>{@code
  Method factoryMethod = Person.class.getMethod("create");
  Invokable<?, Person> factory = Invokable.of(getNameMethod).returning(Person.class);
  }</pre>