Data_model not showing the tags from the example

Community Support
1

Hi all !!

I am trying the last release of bokeh 2.3. As explained in github tracking PR of the datamodel, I am trying to use the tags to have sincronized a variable in js and python simultaneously from the JS side. I tried the example in examples/plotting/file/data_model.py but the tags appears empty in JS console.

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I am using bokeh in windows with chrome 88.0.4324.182. The same behavior appears in firefox.

The code is the following

import numpy as np

from bokeh.core.properties import Float
from bokeh.io import save
from bokeh.layouts import column
from bokeh.model import DataModel
from bokeh.models import ColumnDataSource, CustomJS
from bokeh.plotting import figure, curdoc


class Params(DataModel):
    amp = Float(default=0.1, help="Amplitude")
    freq = Float(default=0.1, help="Frequency")
    phase = Float(default=0, help="Phase")
    offset = Float(default=-5, help="Offset")

params = Params(amp=2, freq=3, phase=0.4, offset=1)

A = params.amp
k = params.freq
phi = params.phase
B = params.offset
x = np.linspace(0, 10, 100)
y = A*np.sin(k*x + phi) + B

source = ColumnDataSource(data=dict(x=x, y=y))

plot = figure(tags=[params],y_range=(-10, 10), title="Data models example")

plot.line("x", "y", source=source, line_width=3, line_alpha=0.6)

callback = CustomJS(args=dict(source=source, params=params), code="""
    const data = source.data
    const A = params.amp
    const k = params.freq
    const phi = params.phase
    const B = params.offset
    const {x, y} = data
    for (let i = 0; i < x.length; i++) {
        y[i] = A*Math.sin(k*x[i] + phi) + B
    }
    source.change.emit()
""")

params.js_on_change("amp", callback)
params.js_on_change("freq", callback)
params.js_on_change("phase", callback)
params.js_on_change("offset", callback)

curdoc().add_root(column(plot))

thanks for all your work,

Best regards,
Néstor