散景悬停工具提示问题：显示“ ???”

Question

我是Bokeh的新手，正在尝试学习如何使用悬停工具。情节显示不是显示我想要的内容，而是显示??? （请参见下文）

import numpy as np
import pandas as pd
from bokeh.plotting import figure, output_file,show
from bokeh.io import show, output_notebook
from bokeh.models import ColumnDataSource, HoverTool
from bokeh.sampledata.iris import flowers

colormap = {'setosa': 'red', 'versicolor': 'green', 'virginica': 'blue'}

colors = [colormap[x] for x in flowers['species']]

TOOLTIPS = [
    ("index", "$index"),
    ("(x,y)", "($x, $y)"),
    ("species", "@species"),
]

p = figure(title = "Iris Morphology",
           tools="pan,lasso_select,box_select,hover",
           tooltips=TOOLTIPS)
p.xaxis.axis_label = 'Petal Length'
p.yaxis.axis_label = 'Petal Width'

p.circle(flowers["petal_length"], flowers["petal_width"],
         color=colors, fill_alpha=0.2, size=10)

# Set to output the plot in the notebook
output_notebook()

# Show the plot
show(p)

我已经研究了解决方案（见下文），但找不到答案。

In Bokeh, how do I add tooltips to a Timeseries chart (hover tool)?

Bokeh hover tooltip not displaying all data - Ipython notebook

谢谢！