static string GetBaseTypeExpression(CodeTypeDeclaration typeDeclaration)
        {
            var baseTypes = typeDeclaration.BaseTypes
                            .OfType <CodeTypeReference>()
                            .Where(reference => TypeMapper.IsValidTypeForDerivation(reference))
                            .Select(reference => TypeMapper.MapCodeTypeReferenceToTsText(reference))
                            .ToList();

            if (baseTypes.Any() && !typeDeclaration.IsEnum)
            {
                return($" extends {string.Join(",", baseTypes)}");
            }

            return(String.Empty);
        }