public Deque<String>  getCopyOfDequeByKey(String key) {
        if (getMDCAdapter() == null) {
            throw new IllegalStateException(MDC_APAPTER_CANNOT_BE_NULL_MESSAGE);
        }
        return getMDCAdapter().getCopyOfDequeByKey(key);
    }
Returns a copy of the deque(stack) referenced by 'key'. May be null.

@param key identifies the  stack
@return copy of stack referenced by 'key'. May be null.

@since 2.0.0
slf4j-api/src/main/java/org/slf4j/MDC.java