private IMagickImage ExecuteCombine(XmlElement element, IMagickImageCollection collection)
        {
            Hashtable arguments = new Hashtable();

            foreach (XmlAttribute attribute in element.Attributes)
            {
                arguments[attribute.Name] = Variables.GetValue <ColorSpace>(attribute);
            }
            if (arguments.Count == 0)
            {
                return(collection.Combine());
            }
            else if (OnlyContains(arguments, "colorSpace"))
            {
                return(collection.Combine((ColorSpace)arguments["colorSpace"]));
            }
            else
            {
                throw new ArgumentException("Invalid argument combination for 'combine', allowed combinations are: [] [colorSpace]");
            }
        }