public void FilterByAdditionalFilters_SkipsNullValues()
        {
            lookup.Filter.AdditionalFilters.Add(nameof(TestModel.Id), null);

            IQueryable <TestModel> actual   = lookup.FilterByAdditionalFilters(lookup.GetModels());
            IQueryable <TestModel> expected = lookup.GetModels();

            Assert.Equal(expected, actual);
        }