Working through the Panel user guide - any example on this page (<https://panel.pyviz.org/user_guide/Components.html>) that uses .extend does not seem to be working and is returning

```
AttributeError: 'Tabs' object has no attribute 'extend'

```

And the gridspec example returns:

```
AttributeError: module 'panel' has no attribute 'GridSpec'

```

Currently using Panel 0.3.1

Ben