private void updateLabelPanel() {
        labelPanel.clear();
        if (NullSafe.isNonBlankString(formLabel.getLabel())) {
            labelPanel.add(formLabel);
        }

        if (helpButton.hasHelpContent()) {
            labelPanel.add(helpButton);
        }
    }
Plain text, any HTML will be escaped.
The helpText attr trumps the {@code <form:HelpHTML>} element.
<p>
To programmatically set HTML help text, use {@link FormGroup#overrideHelpText(SafeHtml)}.
</p>
stroom-core-client-widget/src/main/java/stroom/widget/form/client/FormGroup.java