@Override
        protected Map<String, String> childValue(Map<String, String> parentValue) {
            if (parentValue == null) {
                return null;
            }
            return new HashMap<>(parentValue);
        }
Basic MDC implementation, which can be used with logging systems that lack
out-of-the-box MDC support.

This code was initially inspired by  logback's LogbackMDCAdapter. However,
LogbackMDCAdapter has evolved and is now considerably more sophisticated.

@author Ceki Gulcu
@author Maarten Bosteels
@author Lukasz Cwik

@since 1.5.0
slf4j-api/src/main/java/org/slf4j/helpers/BasicMDCAdapter.java