I was learning plotly dropdown menu and stumbled on a label problem.

Question
========

* How to show labels `sin and sin-1` when selected Sine. And show labels `tan and tan-1` when selected Tan?

MWE
===

```py
# imports
import plotly.graph_objects as go
import numpy as np

# data
x = np.linspace(-np.pi, np.pi, 100)

y1 = np.sin(x)
y1b = y1-1

y2 = np.tan(x)
y2b = y2-1

# plotly setup
fig = go.Figure()

# Add one ore more traces
fig.add_traces(go.Scatter(x=x, y=y1,name='sin'))
fig.add_traces(go.Scatter(x=x, y=y1b,name='sin - 1'))

fig.add_traces(go.Scatter(x=x, y=y2,name='tan'))
fig.add_traces(go.Scatter(x=x, y=y2b,name='tan - 1'))

# construct menus
updatemenus = [{'buttons': [{'method': 'update',
                             'label': 'Sine',
                             'args': [{'y': [y1, y1b]},]
                              },
                            {'method': 'update',
                             'label': 'Tan',
                             'args': [
                                 {'y': [y2, y2b],'label':['a','b']},
                             ]}
                           ],
                'direction': 'down',
                'showactive': True,}]

# update layout with buttons, and show the figure
fig.update_layout(updatemenus=updatemenus)
fig.show()

```

output
======

[![enter image description here](https://i.stack.imgur.com/dz8p2.png)](https://i.stack.imgur.com/dz8p2.png)