Figures in Output disappear if Output displayed twice in same cell

Riproduci il problema con l’esempio di notebook Python fornito, chiamando display(o) due volte dopo aver creato una figura matplotlib all’interno di un widget Output. Confronta la prima e la seconda visualizzazione usando le versioni elencate di JupyterLab, ipympl, matplotlib e ipywidgets; l’attività è completata quando la figura rimane visibile dopo la visualizzazione ripetuta.

Describe the issue

Got an odd one.
If an Output contains a figure, and one calls a single cell containing display(Output) twice, the output "empties" and no figure is shown.

Example below. One can emphasise it by first calling display(o) in one cell, and then doing the double call (I press ctrl + Enter twice) in another cell. I attach a figure showing the result.

# in one cell:
%matplotlib widget
import matplotlib.pyplot as plt
from ipywidgets import Output
o = Output()
with o:
    plt.figure()
    plt.plot([1,2,3])
# In a separate cell, call this twice after each other
display(o)

Versions

 3.8.2 | packaged by conda-forge | (default, Mar 23 2020, 17:32:17) [MSC v.1916 64 bit (AMD64)]
ipympl version: 0.5.6
jupyter core     : 4.6.3
jupyter-notebook : 6.0.3
qtconsole        : 4.7.2
ipython          : 7.13.0
ipykernel        : 5.2.0
jupyter client   : 6.1.3
jupyter lab      : 2.1.4
nbconvert        : 5.6.1
ipywidgets       : 7.5.1
nbformat         : 5.0.4
traitlets        : 4.3.3
Known nbextensions:
  config dir: C:\Users\thomasaar\.jupyter\nbconfig
    notebook section
      default_cells disabled
  config dir: C:\Users\thomasaar\.conda\envs\py5\etc\jupyter\nbconfig
    notebook section
      ipyvolume/extension enabled
      - Validating: ok
      jupyter-webrtc/extension enabled
      - Validating: ok
      jupyter-matplotlib/extension enabled
      - Validating: ok
      plotlywidget/extension enabled
      - Validating: ok
      jupyter-js-widgets/extension enabled
      - Validating: ok
    tree section
      ipyparallel/main enabled
      - Validating: ok
JupyterLab v2.1.4
Known labextensions:
   app dir: C:\Users\thomasaar\.conda\envs\py5\share\jupyter\lab
        @jupyter-widgets/jupyterlab-manager v2.0.0 enabled  ok
        @jupyter-widgets/jupyterlab-sidecar v0.5.0 enabled  ok
        jupyter-matplotlib v0.7.2 enabled  ok```