private Optional<String> getAttribute(final AttributeMap attributeMap, final CIKey header) {
        if (header == null) {
            return Optional.empty();
        }
        return Optional.ofNullable(attributeMap.get(header.get()))
                .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