message: [bugfix] add support for numeric nodes in Sankey
  * [bugfix] add support for numeric nodes in Sankey
  closes
  * lint
diff: @@ -31,6 +31,7 @@ from markdown import markdown
  import numpy as np
  import pandas as pd
  from pandas.tseries.frequencies import to_offset
  +from past.builtins import basestring
  import polyline
  import simplejson as json
  from six import string_types, text_type
  @@ -1596,6 +1597,8 @@ class SankeyViz(BaseViz):
  def get_data(self, df):
  df.columns = ['source', 'target', 'value']
  + df['source'] = df['source'].astype(basestring)
  + df['target'] = df['target'].astype(basestring)
  recs = df.to_dict(orient='records')
  hierarchy = defaultdict(set)
  