[Bug][Jupyter Widget] Error displaying widget: model not found (still)

**Description**
I have been struggling with the problem described in [this issue](https://github.com/keplergl/kepler.gl/issues/1064) and [this one](https://github.com/keplergl/kepler.gl/issues/570) for a few days now. I've tried the instructions but they don't seem to fix the problem. I can't reopen the issue so I have created a new one here.

**To Reproduce**
When I type:
```
from keplergl import KeplerGl
map_1 = KeplerGl()
map_1
```
I get:
```
User Guide: https://docs.kepler.gl/docs/keplergl-jupyter
Error displaying widget: model not found
```
Developer console error:
```
manager.js:319 Uncaught (in promise) Error: Module keplergl-jupyter, semver range ^0.2.0 is not registered as a widget module
at WidgetManager.loadClass (manager.js:319)
at WidgetManager. (manager-base.js:264)
at step (manager-base.js:45)
at Object.next (manager-base.js:26)
at manager-base.js:20
at new Promise ()
at push.SEna.__awaiter (manager-base.js:16)
at WidgetManager.push.SEna.ManagerBase._make_model (manager-base.js:258)
at WidgetManager. (manager-base.js:247)
at step (manager-base.js:45)
```
**Expected behavior**
I expect to see a slippy map.

**Environment (please complete the following information):**
- Python 3.6.8
- Windows 10
`jupyter --version`

```
jupyter core : 4.6.3
jupyter-notebook : 6.0.3
qtconsole : 4.7.5
ipython : 7.15.0
ipykernel : 5.3.0
jupyter client : 6.1.3
jupyter lab : 2.1.4
nbconvert : 5.6.1
ipywidgets : 7.5.1
nbformat : 5.0.6
traitlets : 4.3.3
```

`jupyter labextension list`

```
JupyterLab v2.1.4
Known labextensions:
app dir: C:\Users\[USER]\.conda\envs\py36\share\jupyter\lab
@jupyter-widgets/jupyterlab-manager v2.0.0 enabled ok
@jupyterlab/toc v3.0.0 enabled ok
js v0.1.0 enabled ok
jupyter-gmaps v0.9.0 enabled ok
jupyter-leaflet v0.13.0 enabled ok
jupyterlab-jupytext v1.2.1 enabled ok
jupyterlab-stata-highlight v0.1.1 enabled ok
keplergl-jupyter v0.2.0 enabled ok
```

**Additional context**
The problem seems to affect any extensions with a slippy map, including gmaps and ipyleaflet. I believe it arose when I downloaded and started to use kepler (probably from updating some packages in the process?) since gmaps used to work. To be clear, it's fine in Jupyter notebook, just not in lab.

Any thoughts would be much appreciated!