Fastcore

New Features

- Add `ft_cls` to `ft` ([620](https://github.com/fastai/fastcore/issues/620))

New Features

- Add module `__getattr__` to `fastcore.xml` ([619](https://github.com/fastai/fastcore/issues/619))

Bugs Squashed

- Curried `risinstance` fails when passed `None` ([618](https://github.com/fastai/fastcore/issues/618))

New Features

- Add `AttrDictDefault` and `extract_docstrings` ([617](https://github.com/fastai/fastcore/issues/617))
- Add `do_escape` to `to_xml` ([617](https://github.com/fastai/fastcore/issues/617))
- add markdown to doc output ([614](https://github.com/fastai/fastcore/issues/614))
- move patched methods to parent class ([612](https://github.com/fastai/fastcore/pull/612)), thanks to [comhar](https://github.com/comhar)
- add debug=True parameter to urlsend ([611](https://github.com/fastai/fastcore/pull/611)), thanks to [radam9](https://github.com/radam9)

Bugs Squashed

- fix annotations generated by py2pyi ([613](https://github.com/fastai/fastcore/pull/613)), thanks to [comhar](https://github.com/comhar)

New Features

- Add `UNSET` singleton
- nullable dataclass overhaul ([607](https://github.com/fastai/fastcore/issues/607))
- Update `nullable_dc` to use `UNSET` instead of `None`
- Rename `mk_dataclass` to `flexiclass`
- `flexiclass` uses `UNSET` instead of `None`
- Add `asdict`, like the `dataclasses` version but works on more types
- Add `is_typeddict` and `is_namedtuple`
- Flatten nested tuples in `ft`

Breaking Changes

- The FT structure has been changed so it no longer inherits from `list` ([606](https://github.com/fastai/fastcore/issues/606))
- `.list` property added so you can still destructure it
- `__getitem__` now returns the approach child element
- `__add__` adds children