Python holoviews object error

import pandas as pd
import holoviews as hv
from holoviews import opts, dim
from bokeh.sampledata.les_mis import data

# trying to use different data here
data={'nodes':[{'name': 'Fred',         'group': 1},
               {'name': 'Barney',         'group': 1},
               {'name': 'Wilma',      'group': 1},
               {'name': 'Betty',     'group': 1}
               ],
    'links': [{'source': 1, 'target': 0, 'value': 1},
              {'source': 2, 'target': 0, 'value': 1},
              {'source': 2, 'target': 1, 'value': 1},
              {'source': 3, 'target': 3, 'value': 5}
              ] }
ob=hv.Chord(links)
nodes = hv.Dataset(pd.DataFrame(data['nodes']), 'index')
chord = hv.Chord((links, nodes)).select(value=(5, None))
ob=chord.opts(
    opts.Chord(cmap='Category20', edge_cmap='Category20', edge_color=dim('source').str(),
               labels='name', node_color=dim('index').str()))

hv.save(ob,'out2.html')