Marks an object's __toString() method as returning markup.
Objects that implement this interface will not be automatically XSS filtered by the render system or automatically escaped by the theme engine.
If there is any risk of the object's __toString() method returning user-entered data that has not been filtered first, it must not be used. If the object that implements this does not perform automatic escaping or filtering itself, then it must be marked as "@internal". For example, Views has th