* Add flatten_sentinal
* Add FlattenSentinal to __all__
* Fix lint errors
* Fix type errors
* Update test to use leave_Return
* Update and run codegen
* Add empty test
* Update docs
* autofix
Add a RemoveFromParent() function as a convenience to returning RemovalSentinel.REMOVE.
Introduce a `deep_remove()` on CSTNode analogous to `deep_replace()` but for removing.
These were referred to by other parts of the documentation, and they
provide core parts of our functionality, so we should have explicit
documentation for them.
- Now that we're exporting everything from the top-level libcst package,
automodule makes a mess of things.
- While it does create more boilerplate, using autoclass/autofunction
instead of automodule gives us a lot more control over the order in
which nodes are presented, so we can group them by various categories.
This diff also exports BaseParenthesizableWhitespace, because nodes
refer to it by type, and so it's needed for documentation purposes.
