Document any special tokens this field might use for itself.
Overrides FieldPluginBase::document_self_tokens
add_self_tokens()
function document_self_tokens(&$tokens) {
$tokens['[' . $this->options['id'] . '-role' . ']'] = t('The name of the role.');
$tokens['[' . $this->options['id'] . '-rid' . ']'] = t('The role machine-name of the role.');
}