must specify renderer for showing Plotly graphs

[butterlyn]

Please add to the documentation that you must specify the "notebook" renderer for plotly to work.

For example:

import plotly.express as px
df = px.data.iris()
fig = px.scatter(df, x="sepal_width", y="sepal_length")
fig.show(renderer="notebook")

The example code in the demo project no longer works without specifying the renderer.