While trying to solve this issue http://forum.plantuml.net/6341, I created this diagram:
http://www.plantuml.com/plantuml/uml/SoWkIImgAStDuG8pkAmSaqioy_EikHGKqlABie6KWWAQc49YUc9c7l4o2Whf-INv2ebW0IEWG6fU2iJmdCIar1ou15IBWf4rbmDG2T1D0000
which gives:
(--------)