ctionary.
       *
       * Valid configuration in `options` are as follows:
       *
       * - `forwardHostProp(property, value)`: Called when a property referenced
       *   in the template changed on the template's host. As this library does
       *   not retain references to templates instanced by the user, it is the
       *   templatize owner's responsibility to forward host property changes into
       *   user-stamped instances.  The `instance.forwardHostProp(property, value)`
       *    method 