# Bug with DeserializationError when changing content layout in Bokeh 3.1.1

**URL:** <https://discourse.bokeh.org/t/bug-with-deserializationerror-when-changing-content-layout-in-bokeh-3-1-1/10566>\
**Category:** Community Support\
**Created:** [June 19, 2023, 1:40pm UTC](https://discourse.bokeh.org/t/bug-with-deserializationerror-when-changing-content-layout-in-bokeh-3-1-1/10566 "2023-06-19T13:40:17Z")\
**Posts on this page:** 1\
**Showing post:** 3

<div class="post-metadata">

**Author:** ![Aziuth](https://discourse.bokeh.org/user_avatar/discourse.bokeh.org/aziuth/32/6060_2.png) [@Aziuth](https://discourse.bokeh.org/u/Aziuth)\
**Post date:** [June 19, 2023, 2:32pm UTC](https://discourse.bokeh.org/t/bug-with-deserializationerror-when-changing-content-layout-in-bokeh-3-1-1/10566/3 "2023-06-19T14:32:10Z")

</div>

Took me a while to assemble one, given that my actual code is a big bulk, but here it is.  
Supposed to be executed as a Bokeh server.

To produce the bug, change the value of the range slider _twice_.

```auto
from bokeh.plotting import figure, curdoc
from bokeh.models import ColumnDataSource, Label, RangeSlider
from bokeh.layouts import column
from random import *

def loading_pic(width: int = 500, height: int = 500) -> figure:
    plot = figure(x_range=(0,width), y_range=(0,height), width=width, height=height, tools='')
    pos_x = width/2 
    pos_y = height/2    
    
    label_size = min(height/4, width/4)
    label_size_str = str(label_size)+'px'
    
    loading_label = Label(x=pos_x, y=pos_y, text='Loading', text_font_size = label_size_str,
                          text_align='center', text_baseline='middle')
    plot.add_layout(loading_label)
    
    plot.xaxis.visible = False
    plot.yaxis.visible = False
    plot.xgrid.grid_line_color = None
    plot.ygrid.grid_line_color = None
    
    return plot
    
def random_coords(maximum: float = 500, amount: int = 1000) -> ColumnDataSource:
    data = ColumnDataSource()
    data.data['x'] = [random()*maximum for i in range(amount)]
    data.data['y'] = [random()*maximum for i in range(amount)]
    return data
    
class MyPlot:
    
    def __init__ (self, data: ColumnDataSource):
        self.plot = figure(x_range=(0,500), y_range=(0,500), width=500, height=500)
        self.plot.circle(source=data, x='x', y='y')
    
class MyFrame:

    def __init__ (self):
        self.layout = column()
        self.loading = loading_pic()
        self.layout.children.append(self.loading)

    def display_loading(self) -> None:
        self.layout.children[0] = self.loading

    def plot(self, data) -> None:
        self.my_plot = MyPlot(data)
        self.layout.children[0] = self.my_plot.plot
        
    def plot_delayed(self, attr, old, new) -> None:
        self.display_loading()
        data = random_coords()
        curdoc().add_next_tick_callback(lambda: self.plot(data)) 
        
my_frame = MyFrame()
        
range_slider = RangeSlider(start = 0, end = 10, value = (0,10), step = 1, title = 'Range')
range_slider.on_change('value_throttled', my_frame.plot_delayed)
       
layout = column(my_frame.layout, range_slider)

curdoc().add_root(layout)

```

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