public void AddDefaultFacetsIfMissing(List <string> additionalFacets)
        {
            var defaultFacets = new List <string> {
                "theme", "type", "organization"
            };

            if (additionalFacets.Any())
            {
                defaultFacets.AddRange(additionalFacets);
            }

            foreach (var defaultFacet in defaultFacets)
            {
                if (Facets.All(f => f.Name != defaultFacet))
                {
                    Facets.Add(new FacetParameter {
                        Name = defaultFacet
                    });
                }
            }
        }