title: Hover ToolTip Not Working for Bokeh visualization of Networkx Graph
body: <p>I'm trying to make graph using Networkx and rendering the graph using Bokeh. Everything seems to be working except for the hover tooltip I've consulted <a href="https://stackoverflow.com/questions/33022985/data-tooltips-in-bokeh-dont-show-data-showing-instead">Data tooltips in Bokeh don&#39;t show data, showing &#39;???&#39; instead</a>, <a href="https://stackoverflow.com/questions/31226119/bokeh-hover-tooltip-not-displaying-all-data-ipython-notebook">Bokeh hover tooltip not displaying all data - Ipython notebook</a>, and read the documentation on ColumnDataSource, but i still can't figure out why tooltips won't render labels from one of the columns of my dataframe.</p>
  
  <p>Below is a overly simplified of the data from an excel file, which I've been playing around with.</p>
  
  <pre><code>group    subtopic    code
  fruit    grapes      110A
  fruit    apple       110B
  meat     pork        220A
  meat     chicken     220B
  meat     duck        220C
  vegetable lettuce    300A
  vegetable tomato     310A
  vegetable asparagus  320A
  </code></pre>
  
  <p>I tried running the following code:</p>
  
  <pre><code>df = pd.read_excel(file1, sheetname = 'Sheet3')
  
  reshape = []
  
  for i, j, in df.iterrows():
      for _, k in df.iterrows():
          if (j['code'] == k['code']):
              pass
          elif j['group'] == 'nan':
              reshape.append({'code1':j['code'],
                         'code2': j['code'],
                         'group': 'None'})
          elif (j['group'] == k['group']):
              reshape.append({'code1': j['code'],
                         'code2': k['code'],
                         'group': j['group']})
          else:
              pass
  df1 = pd.DataFrame(reshape)
  
  g = nx.from_pandas_edgelist(df1, source='code1', target='code2', edge_attr = True)
  
  
  source = ColumnDataSource(df)
  
  TOOLTIPS = [("type", "@group"),("code", "@code1")]
  
  plot = Plot(x_range = Range1d(-1.1,1.1), y_range = Range1d(-1.1,1.1))
  plot.title.text = 'Bokeh Plot'
  
  plot.add_tools(HoverTool(tooltips = TOOLTIPS), TapTool(), BoxSelectTool(), 
   WheelZoomTool())
  
  graph_renderer = from_networkx(g, nx.spring_layout, scale = 1, center = (0,0))
  
  # manipulating nodes
  graph_renderer.node_renderer.glyph = Circle(size = 15, fill_color = Spectral4[0])
  graph_renderer.node_renderer.selection_glyph = Circle(size = 15, fill_color = 
   Spectral4[2])
  graph_renderer.node_renderer.hover_glyph = Circle(size = 15, fill_color = 
   Spectral4[1])
  
  # manipulating edges
  graph_renderer.edge_renderer.glyph = MultiLine(line_color = '#CCCCCC', line_alpha = 
   .5, line_width = 5)
  graph_renderer.edge_renderer.selection_glyph = MultiLine(line_color = Spectral4[2], 
   line_width = 5)
  graph_renderer.edge_renderer.hover_glyph = MultiLine(line_color = Spectral4[1], 
   line_width = 5)
  
  graph_renderer.selection_policy = NodesAndLinkedEdges()
  graph_renderer.inspection_policy = EdgesAndLinkedNodes()
  
  plot.renderers.append(graph_renderer)
  
  output_notebook()
  show(plot)
  </code></pre>
  
  <p>After I run the script, i get the following:</p>
  
  <p><a href="https://i.stack.imgur.com/2KS56.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2KS56.png" alt="screenshit"></a>
  The group column label correctly displays, but not the subtopic. I'd appreciate any ideas or pointers. </p>