@Override
    public boolean exist(ClassLoader classLoader, String className, ProtectionDomain protectionDomain) {
        checkOpen();
        return instrumentContext.exist(classLoader, className, protectionDomain);
    }
@author Woonduk Kang(emeroad)
@author jaehong.kim
agent-module/profiler/src/main/java/com/navercorp/pinpoint/profiler/instrument/GuardInstrumentContext.java