@Override
    public PCollectionsImmutableNavigableSet<E> removed(E e) {
        return new PCollectionsImmutableNavigableSet<>(underlying().minus(e));
    }
@Test
    public void testDelegationOfRemoved() {
        new PCollectionsTreeSetWrapperDelegationChecker<>()
                .defineMockConfigurationForFunctionInvocation(mock -> mock.minus(eq(10)), SINGLETON_SET)
                .defineWrapperFunctionInvocationAndMockReturnValueTransformation(wrapper -> wrapper.removed(10), identity())
                .expectWrapperToWrapMockFunctionReturnValue()
                .doFunctionDelegationCheck();
    }