Visualizations with BokehJS are doubling

Today when booting up my ML environment, I am seeing a doubling of Bokeh visuals:



These are samples from the [Bokeh Jupyter Notebooks samples](https://hub.gke2.mybinder.org/user/bokeh-bokeh-notebooks-385m2jz1/notebooks/tutorial/00%20-%20Introduction%20and%20Setup.ipynb). I have tried restarting my compute and switching to a different compute, but see the same result

```
from bokeh.io import output_notebook, show
output_notebook()
```

```
# Plot a complex chart with interactive hover in a few lines of code

from bokeh.models import ColumnDataSource, HoverTool
from bokeh.plotting import figure
from bokeh.sampledata.autompg import autompg_clean as df
from bokeh.transform import factor_cmap

df.cyl = df.cyl.astype(str)
df.yr = df.yr.astype(str)

group = df.groupby(by=['cyl', 'mfr'])
source = ColumnDataSource(group)

p = figure(plot_width=800, plot_height=300, title="Mean MPG by # Cylinders and Manufacturer",
x_range=group, toolbar_location=None, tools="")

p.xgrid.grid_line_color = None
p.xaxis.axis_label = "Manufacturer grouped by # Cylinders"
p.xaxis.major_label_orientation = 1.2

index_cmap = factor_cmap('cyl_mfr', palette=['#2b83ba', '#abdda4', '#ffffbf', '#fdae61', '#d7191c'],
factors=sorted(df.cyl.unique()), end=1)

p.vbar(x='cyl_mfr', top='mpg_mean', width=1, source=source,
line_color="white", fill_color=index_cmap,
hover_line_color="darkgrey", hover_fill_color=index_cmap)

p.add_tools(HoverTool(tooltips=[("MPG", "@mpg_mean"), ("Cyl, Mfr", "@cyl_mfr")]))

show(p)
```

使用所示的 output_notebook() 和 show(p) 進入點，在連結的 Bokeh Jupyter Notebook 範例中重現問題。將呈現後的視覺化結果與兩張螢幕擷取畫面進行比較，並先確認重複是否來自 notebook 環境或 BokehJS 整合；範例只呈現一次即表示完成。

由索引模型根據 Issue 內容生成。