question: private String findLastStringAssignment ( Stmt stmt , Local local , BiDiInterproceduralCFG < Unit , SootMethod > cfg ) { if ( stmt instanceof AssignStmt ) { AssignStmt assign = ( AssignStmt ) stmt ; if ( assign . getLeftOp ( ) == local ) { if ( assign . getRightOp ( ) instanceof StringConstant ) return ( ( StringConstant ) assign . getRightOp ( ) ) . value ; } } for ( Unit pred : cfg . getPredsOf ( stmt ) ) { if ( ! ( pred instanceof Stmt ) ) continue ; String lastAssignment = findLastStringAssignment ( ( Stmt ) pred , local , cfg ) ; if ( lastAssignment != null ) return lastAssignment ; } return null ; }
target:  Finds the last assignment to the given String local by searching upwards from the given statement