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* Add documentation for methods :meth:`RecordList.exists` and
:meth:`RecordList.ensure_one`.
* Add documentation for methods :meth:`RecordList.mapped`,
:meth:`RecordList.filtered` and :meth:`RecordList.sorted`.
* Add documentation for methods :meth:`Model.with_env`,
:meth:`Model.sudo` and :meth:`Model.with_context`. These methods
are also available on :class:`RecordList` and :class:`Record`.
* Changed method ``exists`` on :class:`RecordList` and :class:`Record`
to return record(s) instead of ids.
* Fix methods ``mapped``, ``filtered`` and ``sorted``. Add tests.
* Fix method ``RecordList.ensure_one()`` when there's identical ids
or ``False`` values.
* Fix method ``RecordList.union(...)`` and related boolean operations.