public object Execute(Expression expression, bool isEnumerable)
        {
            var visitor = new Visitor.RequestExpressionVisitor(expression);

            visitor.Visit();
            Operations = visitor.Operations;
            var rt       = visitor.GetReturnType();
            var type     = typeof(List <>).MakeGenericType(rt);
            var instance = CreateInstance(type);

            return(instance);
        }