[Python] How to make the Holoviews show graph on Google Colaboratory notebook?

I tried all three backends but didn't show any graph. An example is:

!pip install -q holoviews

import holoviews as hv
from holoviews import opts

hv.extension('matplotlib')


# build a dataset where multiple columns measure the same thing
stamp = [.33, .33, .34, .37, .37, .37, .37, .39, .41, .42,
.44, .44, .44, .45, .46, .49, .49]
postcard = [.20, .20, .21, .23, .23, .23, .23, .24, .26, .27,
.28, .28, .29, .32, .33, .34, .35]

group = "U.S. Postage Rates (1999-2015)"
stamp = hv.Curve(stamp, vdims='Rate per ounce', label='stamp', group=group)
postcard = hv.Curve(postcard, vdims='Rate per ounce', label='postcard', group=group)
postage = (stamp * postcard)

postage.opts(
opts.Curve(interpolation='steps-mid', linestyle=hv.Cycle(values=['--', '-'])),
opts.Overlay(legend_position='top_left'))


The code can run but won't draw any graph in the result.

Continue reading...