chore: import upstream snapshot with attribution

docs/md/how_to/python/jupyterlab.md

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+# `PerspectiveWidget` for JupyterLab
+
+Building on top of the API provided by `perspective.Table`, the
+`PerspectiveWidget` is a JupyterLab plugin that offers the entire functionality
+of Perspective within the Jupyter environment. It supports the same API
+semantics of `<perspective-viewer>`, along with the additional data types
+supported by `perspective.Table`. `PerspectiveWidget` takes keyword arguments
+for the managed `View`:
+
+```python
+from perspective.widget import PerspectiveWidget
+w = perspective.PerspectiveWidget(
+    data,
+    plugin="X Bar",
+    aggregates={"datetime": "any"},
+    sort=[["date", "desc"]]
+)
+```
+
+## Creating a widget
+
+A widget is created through the `PerspectiveWidget` constructor, which takes as
+its first, required parameter a `perspective.Table`, a dataset, a schema, or
+`None`, which serves as a special value that tells the Widget to defer loading
+any data until later. In maintaining consistency with the Javascript API,
+Widgets cannot be created with empty dictionaries or lists — `None` should be
+used if the intention is to await data for loading later on. A widget can be
+constructed from a dataset:
+
+```python
+from perspective.widget import PerspectiveWidget
+PerspectiveWidget(data, group_by=["date"])
+```
+
+.. or a schema:
+
+```python
+PerspectiveWidget({"a": int, "b": str})
+```
+
+.. or an instance of a `perspective.Table`:
+
+```python
+table = perspective.table(data)
+PerspectiveWidget(table)
+```
+
+## Updating a widget
+
+`PerspectiveWidget` shares a similar API to the `<perspective-viewer>` Custom
+Element, and has similar `save()` and `restore()` methods that
+serialize/deserialize UI state for the widget.
+
+<!--
+## `PerspectiveRenderer`
+
+Perspective also exposes a JS-only `mimerender-extension`. This lets you view
+`csv`, `json`, and `arrow` files directly from the file browser. You can see
+this by right clicking one of these files and `Open With->CSVPerspective` (or
+`JSONPerspective` or `ArrowPerspective`). Perspective will also install itself
+as the default handler for opening `.arrow` files. -->