private Optional<String> getAttribute(final AttributeMap attributeMap, final String header) {
        return Optional.ofNullable(attributeMap.get(header))
                .filter(StringUtils::isNotBlank);
    }
@return An optional containing a non-blank attribute value, else empty.
stroom-receive/stroom-receive-common/src/main/java/stroom/receive/common/DataFeedKeyServiceImpl.java