标签在我的图形中使用mpld3不可见

Question

我在以下链接中使用mpld3示例： enter link description here

这是确切的代码：

import matplotlib.pyplot as plt
import numpy as np
import pandas as pd
import mpld3
from mpld3 import plugins
np.random.seed(9615)

# generate df
N = 100
df = pd.DataFrame((.1 * (np.random.random((N, 5)) - .5)).cumsum(0),
                  columns=['a', 'b', 'c', 'd', 'e'],)

# plot line + confidence interval
fig, ax = plt.subplots()
ax.grid(True, alpha=0.3)

for key, val in df.iteritems():
    l, = ax.plot(val.index, val.values, label=key)
    ax.fill_between(val.index,
                    val.values * .5, val.values * 1.5,
                    color=l.get_color(), alpha=.4)

# define interactive legend

handles, labels = ax.get_legend_handles_labels() # return lines and labels
interactive_legend = plugins.InteractiveLegendPlugin(zip(handles,
                                                         ax.collections),
                                                     labels,
                                                     alpha_unsel=0.5,
                                                     alpha_over=1.5, 
                                                     start_visible=True)
plugins.connect(fig, interactive_legend)

ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_title('Interactive legend', size=20)

mpld3.show()

为什么我看不到标签“ a”，“ b”，“ c”，“ d”和“ e”？

当我双击它时，我可以看到它在那里（谷歌词典工具看到了它！）。