[From string (line 9) ]                                                                
                                                                                       
@startuml                                                                              
!pragma teoz true                                                                      
skinparam maxMessageSize 150                                                           
!unquoted function DRAW($x) return %set_variable_value($x, 1)                          
!function addActor($part, $actor, $as)                                                 
    !if %variable_exists($part)                                                        
        actor "$actor" as $as                                                          
    !endif                                                                             
!endfunction                                                                           
^^^^^                                                                                  
 This function does not have any !return directive. Declare it as a procedure instead ?