(Python plotly) How to fix local radius of the tubes in a Streamtube plot?

In a Streamtube plot of Python plotly, how do you fix the radius of the tube and not let it vary by the divergence of the field?

Run the following code as shown in this page:

import plotly.graph_objects as go
import pandas as pd

df = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/streamtube-wind.csv').drop(['Unnamed: 0'],axis=1)

fig = go.Figure(data=go.Streamtube(
    x = df['x'],
    y = df['y'],
    z = df['z'],
    u = df['u'],
    v = df['v'],
    w = df['w'],
    starts = dict(
        x = [80] * 16,
        y = [20,30,40,50] * 4,
        z = [0,0,0,0,5,5,5,5,10,10,10,10,15,15,15,15]
    ),
    sizeref = 0.3,
    colorscale = 'Portland',
    showscale = False,
    maxdisplayed = 3000
))

fig.show()

you will see something like:

The radius of the tube varies according to the divergence of the field, according to this documentation. However, this is annoying and I don't want the radius of the tube to vary. I want to fix the radius of the tubes and keep their coloring varying according to the module of the field, as it already does. I don't see any parameter for that in the documentation. I also searched the word "local radius" or "divergence" in the page and found nothing related. This drives me crazy.