def source_photos
      return [] unless sources.kind_of? Array
      @source_photos ||= sources.map do |source| 
        RGallery::Photo.new source.src, options.merge(:sizing => source.sizing)
      end
    end
def source_photos
      return [] unless sources.kind_of? Array
      @source_photos ||= sources.map do |source| 
        RGallery::Photo.new source.src, options.merge(:sizing => source.sizing)
      end
    end
A photo can contain a source set of other photos!