bokeh.client with inherited class

I have inherited the bokeh button class and am trying to get this simple example running with the bokeh server:

import pandas as pd

from bokeh.models import ColumnDataSource

from bokeh.plotting import figure

from bokeh.io import curdoc, push_session

import bokeh.layouts

class BUTTON(bokeh.models.widgets.Button):

"""

This class inherits from bokeh's Button and provides a built in way to add

on_click actions

"""

__subtype__ = 'Dashboard Button'

__view_model__ = 'Button'

def __init__(self, **kwargs):

    super(bokeh.models.widgets.Button, self).__init__(**kwargs)

p = figure()

p.circle([0], [0])

b = BUTTON(label=‘Play’)

view = bokeh.layouts.layout([[b, p]])

doc = curdoc()

#doc.add_root(b) # Note that this line is commented out and so it works!

doc.add_root§

session = push_session(doc)

session.show()

···

So I fire up bokeh serve and then run python example.py which plots a circle. However, if I uncomment the doc.add_root(b) then I get the following server error:

2016-12-30 15:07:40,154 WebSocket connection opened

2016-12-30 15:07:40,154 ServerConnection created

2016-12-30 15:07:40,161 error handling message Message ‘PUSH-DOC’ (revision 1): KeyError(u"View model name ‘Dashboard Button’ not found",)

2016-12-30 15:07:40,235 WebSocket connection closed: code=None, reason=None

Ultimately, I’d like to run this code example from within a jupyter notebook but will settle for running it as above. Any guidance would be greatly appreciated.