Bokeh issue

test.py

import numpy as np

from bokeh.layouts import column, row
from bokeh.models import CustomJS, ColumnDataSource, Slider
from bokeh.plotting import figure, output_file, show

from bokeh.core.property.containers import PropertyValueDict


output_file('test.html')

default_y0 = 0.0
default_y1 = 10.0

N = 10
x = np.linspace(0, 10, N)
y0_arr = default_y0 * np.ones(N)
y1_arr = default_y1 * np.ones(N)

source = ColumnDataSource(data=dict(
    x=x,
    y0=y0_arr,
    y1=y1_arr,
    ))

state = PropertyValueDict(dict(
    y0=default_y0,
    y1=default_y1))


update_plots = """\
    var data = source.data;
    var y0_val = state['y0'];
    var y1_val = state['y1'];

    var x = data['x'];
    var y0 = data['y0'];
    var y1 = data['y1'];

    for (var i = 0; i < x.length; i++) {
        y0[i] = y0_val
        y1[i] = y1_val
    }

    source.change.emit();
"""


def make_change_value_callback(element):
    return CustomJS(args=dict(state=state, source=source), code="""
            state['{}'] = cb_obj.value;
            """.format(element) + update_plots)


y0_slider_callback = make_change_value_callback('y0')
y1_slider_callback = make_change_value_callback('y1')

y0_slider = Slider(start=1, end=100, value=default_y0, step=0.1, title="y0")
y0_slider.js_on_change('value', y0_slider_callback)

y1_slider = Slider(start=1, end=100, value=default_y1, step=0.1, title="y1")
y1_slider.js_on_change('value', y1_slider_callback)


s1 = figure(plot_width=500, plot_height=400, title='test')

s1.line(x='x', y='y0', source=source, line_color='blue', legend='y0')
s1.line(x='x', y='y1', source=source, line_color='red', legend='y1')

show(column(
    row(y0_slider, y1_slider),
    s1
    ))