public String getDisplayValue(final DisplayType displayType) {
        final DisplayType dispType = displayType != null
                ? displayType
                : DisplayType.AUTO;
        final Function<DocRef, String> displayTextFunc = dispType.getDisplayTextFunc();
        return displayTextFunc.apply(this);
    }
@return The name of the 'document' being referenced
stroom-docref/src/main/java/stroom/docref/DocRef.java