question: public void addOperand ( int startTick , int endTick , String text , Lifeline constraintLifeline ) throws SequenceDiagramCheckedException { if ( operands . size ( ) == 0 && this . startTick != startTick ) { throw new IllegalArgumentException ( "The start tick of the first operand must be equal to the start tick of the combined fragment" ) ; } operands . add ( new Operand ( startTick , endTick , text , constraintLifeline ) ) ; }
target:  Adds an operand with an interaction constraint to the combined fragment.