 How to create object and call the function

I can't see any output for this code I know I missing some basic steps like object creation and help on fixing this.  

```python
from pyjamas.ui.SimplePanel import SimplePanel
from pyjamas.ui.HTML import HTML

class HtmlDemo(SimplePanel):
    def __init__(self):
        SimplePanel.__init__(self)

        html = HTML("Hello, <b><i>World!</i></b>")
        self.add(html)
```