Is there a way to specify the equivalent of Graphviz's headlabel/taillabel? I'd like to annotate the arrows on a sequence diagram with line numbers underneath, for the source/destination.
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You can also have
@startuml class foo class dummy foo "1" -- "*" dummy : contains @enduml
http://www.plantuml.com/plantuml/uml/Iyv9B2vMIClFvqe6ir9AStChkO1y1IL39GLTNGKbBIM8e8ALGd9-NabYPbun0000
Is this what you are looking for ?