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+=================
+Typing Extensions
+=================
+
+.. image:: https://badges.gitter.im/python/typing.svg
+ :alt: Chat at https://gitter.im/python/typing
+ :target: https://gitter.im/python/typing?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge
+
+Overview
+========
+
+The ``typing_extensions`` module serves two related purposes:
+
+- Enable use of new type system features on older Python versions. For example,
+  ``typing.TypeGuard`` is new in Python 3.10, but ``typing_extensions`` allows
+  users on Python 3.6 through 3.9 to use it too.
+- Enable experimentation with new type system PEPs before they are accepted and
+  added to the ``typing`` module.
+  
+New features may be added to ``typing_extensions`` as soon as they are specified
+in a PEP that has been added to the `python/peps <https://github.com/python/peps>`_
+repository. If the PEP is accepted, the feature will then be added to ``typing``
+for the next CPython release. No typing PEP has been rejected so far, so we
+haven't yet figured out how to deal with that possibility.
+
+Starting with version 4.0.0, ``typing_extensions`` uses
+`Semantic Versioning <https://semver.org/>`_. The
+major version is incremented for all backwards-incompatible changes.
+Therefore, it's safe to depend
+on ``typing_extensions`` like this: ``typing_extensions >=x.y, <(x+1)``,
+where ``x.y`` is the first version that includes all features you need.
+
+``typing_extensions`` supports Python versions 3.7 and higher. In the future,
+support for older Python versions will be dropped some time after that version
+reaches end of life.
+
+Included items
+==============
+
+This module currently contains the following:
+
+- Experimental features
+
+  - ``@dataclass_transform()`` (see PEP 681)
+
+- In ``typing`` since Python 3.11
+
+  - ``assert_never``
+  - ``assert_type``
+  - ``LiteralString`` (see PEP 675)
+  - ``Never``
+  - ``NotRequired`` (see PEP 655)
+  - ``reveal_type``
+  - ``Required`` (see PEP 655)
+  - ``Self`` (see PEP 673)
+  - ``TypeVarTuple`` (see PEP 646)
+  - ``Unpack`` (see PEP 646)
+
+- In ``typing`` since Python 3.10
+  
+  - ``Concatenate`` (see PEP 612)
+  - ``ParamSpec`` (see PEP 612)
+  - ``ParamSpecArgs`` (see PEP 612)
+  - ``ParamSpecKwargs`` (see PEP 612)
+  - ``TypeAlias`` (see PEP 613)
+  - ``TypeGuard`` (see PEP 647)
+  - ``is_typeddict``
+
+- In ``typing`` since Python 3.9
+
+  - ``Annotated`` (see PEP 593)
+
+- In ``typing`` since Python 3.8
+
+  - ``final`` (see PEP 591)
+  - ``Final`` (see PEP 591)
+  - ``Literal`` (see PEP 586)
+  - ``Protocol`` (see PEP 544)
+  - ``runtime_checkable`` (see PEP 544)
+  - ``TypedDict`` (see PEP 589)
+  - ``get_origin`` (``typing_extensions`` provides this function only in Python 3.7+)
+  - ``get_args`` (``typing_extensions`` provides this function only in Python 3.7+)
+
+- In ``typing`` since Python 3.7
+
+  - ``OrderedDict``
+
+- In ``typing`` since Python 3.5 or 3.6 (see `the typing documentation
+  <https://docs.python.org/3.10/library/typing.html>`_ for details)
+
+  - ``AsyncContextManager``
+  - ``AsyncGenerator``
+  - ``AsyncIterable``
+  - ``AsyncIterator``
+  - ``Awaitable``
+  - ``ChainMap``
+  - ``ClassVar`` (see PEP 526)
+  - ``ContextManager``
+  - ``Coroutine``
+  - ``Counter``
+  - ``DefaultDict``
+  - ``Deque``
+  - ``NewType``
+  - ``NoReturn``
+  - ``overload``
+  - ``Text``
+  - ``Type``
+  - ``TYPE_CHECKING``
+  - ``get_type_hints``
+
+Other Notes and Limitations
+===========================
+
+Certain objects were changed after they were added to ``typing``, and
+``typing_extensions`` provides a backport even on newer Python versions:
+
+- ``TypedDict`` does not store runtime information
+  about which (if any) keys are non-required in Python 3.8, and does not
+  honor the "total" keyword with old-style ``TypedDict()`` in Python
+  3.9.0 and 3.9.1.
+- ``get_origin`` and ``get_args`` lack support for ``Annotated`` in
+  Python 3.8 and lack support for ``ParamSpecArgs`` and ``ParamSpecKwargs``
+  in 3.9.
+- ``@final`` was changed in Python 3.11 to set the ``.__final__`` attribute.
+
+There are a few types whose interface was modified between different
+versions of typing. For example, ``typing.Sequence`` was modified to
+subclass ``typing.Reversible`` as of Python 3.5.3.
+
+These changes are _not_ backported to prevent subtle compatibility
+issues when mixing the differing implementations of modified classes.
+
+Certain types have incorrect runtime behavior due to limitations of older
+versions of the typing module:
+
+- ``ParamSpec`` and ``Concatenate`` will not work with ``get_args`` and
+  ``get_origin``. Certain PEP 612 special cases in user-defined
+  ``Generic``\ s are also not available.
+
+These types are only guaranteed to work for static type checking.
+
+Running tests
+=============
+
+To run tests, navigate into the appropriate source directory and run
+``test_typing_extensions.py``.