Resize callback not working

Describe the issue

I am having an issue specifically with the Resize callback. The other callback options appear to work as expected. For example replacing 'resize_event' with 'draw_event' in the code block below gives no issues.

import matplotlib.pyplot as plt
import numpy as np
from ipywidgets import Output
%matplotlib widget

output = Output()

@output.capture()
def key_event(event):
    print('action')

fig, ax = plt.subplots()
ax.plot(np.random.rand(10))
fig.canvas.mpl_connect('resize_event', key_event)

display(output)

Versions

3.6.8 (default, Jan 14 2019, 11:02:34) 
[GCC 8.0.1 20180414 (experimental) [trunk revision 259383]]
ipympl version: 0.7.0
jupyter core     : 4.5.0
jupyter-notebook : 6.0.1
qtconsole        : not installed
ipython          : 7.7.0
ipykernel        : 5.1.2
jupyter client   : 5.3.1
jupyter lab      : 1.0.9
nbconvert        : 5.6.0
ipywidgets       : 7.6.3
nbformat         : 4.4.0
traitlets        : 4.3.2
Known nbextensions:
  config dir: /usr/local/etc/jupyter/nbconfig
    notebook section
      ipyvolume/extension  enabled
      - Validating: OK
      jupyter-datawidgets/extension  enabled
      - Validating: OK
      jupyter-matplotlib/extension  enabled
      - Validating: OK
      jupyter-threejs/extension  enabled
      - Validating: OK
      jupyter-webrtc/extension  enabled
      - Validating: OK
      jupyter-js-widgets/extension  enabled
      - Validating: OK
    tree section
      ipyparallel/main  enabled
      - Validating: OK
JupyterLab v1.0.9
Known labextensions:
   app dir: /usr/local/share/jupyter/lab
        jupyter-threejs v2.3.0  enabled  OK
        jupyterlab-datawidgets v7.0.0  enabled  OK

Comienza ejecutando el ejemplo de Jupyter Notebook proporcionado con ipympl 0.7.0 y compara el callback resize_event con draw_event. Sigue el punto de entrada fig.canvas.mpl_connect a través de la integración con el notebook para identificar por qué el cambio de tamaño no llega al callback. La tarea estará terminada cuando el ejemplo imprima action al cambiar el tamaño de la figura, conservando el comportamiento existente del callback.