def __init__(self, app, parent, viewerid=None, viewer_name="viewer"):
gtk.VBox.__init__(self, False, 0)
self._app = app
self._main_window = parent
self._viewerid = viewerid if viewerid else unicode(uuid.uuid4())
self._viewer_name = viewer_name
self._notebook = None
self._history = NodeHistory()
# register viewer
self._main_window.add_viewer(self)
