Log Message:
py-ipywidgets: updated to 7.7.0

7.7
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Highlights include:

- Fix installation on Python 3.10.
- Throw an error if we cannot render a widget, enabling the rendering system to \ 
fall back to rendering a different data type if available.
- Create a new widget control comm channel, enabling more efficient fetching of \ 
kernel widget state.
- Refactor logic for fetching kernel widget state to the manager base class. \ 
This logic first tries to use the new widget control comm channel, falling back \ 
to the existing method of requesting each widget's state individually.
- Enable HTMLManager output widgets to render state updates.
- Do not reset JupyterLab CSS variables if they are already defined.
- Fix variable inspector example.
- Introduce new widget manager `has_model` method for synchronously checking if \ 
a widget model is registered.
- Work around bug in Chrome rendering Combobox arrows.
- Optionally echo update messages from frontends to other frontends. This \ 
enables widget views in different frontends to maintain consistent state \ 
simultaneously, and also makes sure that simultaneous updates from the kernel \ 
and frontend resolve to a consistent state. This is off by default in ipywidgets \ 
7.7, and it is anticipated this will be on by default in ipywidgets 8.0. To \ 
enable echo update messages across ipwyidgets, set the environment variable \ 
`JUPYTER_WIDGETS_ECHO` to 1. To opt a specific attribute out of echo updates, \ 
tag the attribute with `echo_update=False` metadata (we do this in core for the \ 
FileUpload widget's `data` attribute).