@startuml
actor User as A
participant ":Middle" as M
A -> M : op1
activate A
activate M
M -> M : op2
activate M
create "la:Last" as L
M -> L : op3
activate L
L --> M : la
deactivate L
destroy L
M --> M : return
deactivate M
M --> A : return
deactivate M
deactivate A
skinparam sequenceParticipant underline
hide footbox
@enduml
 
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