I'm trying to use `plotly.express` in python to generate a [heatmap](https://plotly.com/python/heatmaps/) from a pandas dataframe with a custom hover template that includes additional variables. So for example:

```
import pandas as pd
import plotly.express as px

df = pd.DataFrame({'A': [10, 11, 12], 'B': [10, 12, 14], 'C': [12, 14, 16]}, 
       index=['joe', 'tom', 'bob'])

fig = px.imshow(df)
fig.update_layout(xaxis={'title': 'Letters'}, yaxis={'title': 'Nicknames'})
fig.show()

```

Gives me this:

[![plotly heatmap](https://i.stack.imgur.com/HBRbF.png)](https://i.stack.imgur.com/HBRbF.png)

What I want is to add or replace a variable in the hover information, for instance, replace the nicknames with Joseph, Thomas and Robert.

This has to be possible, but I can't figure out how to do it with a heatmap. Is there a straight forward way to do this in `plotly.express`? Should I use the "go" interface instead (if so, how)?