@Override
    public Deque<String> getCopyOfDequeByKey(String key) {
        return threadLocalMapOfDeques.getCopyOfDequeByKey(key);
    }
Put a context value (the <code>val</code> parameter) as identified with
the <code>key</code> parameter into the current thread's context map. The
<code>key</code> parameter cannot be null. Log4j does <em>not</em>
support null for the <code>val</code> parameter.

<p>
This method delegates all work to log4j's MDC.

@throws IllegalArgumentException
            in case the "key" or <b>"val"</b> parameter is null
slf4j-reload4j/src/main/java/org/slf4j/reload4j/Reload4jMDCAdapter.java