erwise), the order is deduced from
    the order of the attributes inside *these*.  Otherwise the order
    of the definition of the attributes is used.

:type these: `dict` of `str` to `attr.ib`

:param str repr_ns: When using nested classes, there's no way in Python 2
    to automatically detect that.  Therefore it's possible to set the
    namespace explicitly for a more meaningful ``repr`` output.
:param bool auto_detect: Instead of setting the *init*, *repr*, *eq*,
    *order*, and *hash* arguments explicitly, assume they are set to
    ``True`` **unless any** of the involved methods for one of the
    arguments is implemented in the *current* class (i.e. it is *not*
    inherited from some base class).

    So for example by implementing ``__eq__`` on a class yourself,
    ``attrs`` will deduce ``eq=False`` and will create *neither*
    ``__eq__`` *nor* ``__ne__`` (but Python classes come with a sensible
    ``__ne__`` by default, so it *should* be enough to only implement
    ``__eq__`` in most cases).

    .. warning::

       If you prevent ``attrs`` from creating the ordering methods for you
       (``order=False``, e.g. by implementing ``__le__``), it becomes
       *your* responsibility to make sure its ordering is sound. The best
       way is to use the `functools.total_ordering` decorator.


    Passing ``True`` or ``False`` to *init*, *repr*, *eq*, *order*,
    *cmp*, or *hash* overrides whatever *auto_detect* would determine.

    *auto_detect* requires Python 3. Setting it ``True`` on Python 2 raises
    an `attrs.exceptions.PythonTooOldError`.

:param bool repr: Create a ``__repr__`` method with a human readable
    representation of ``attrs`` attributes..
:param bool str: Create a ``__str__`` method that is identical to
    ``__repr__``.  This is usually not necessary except for
    `Exception`\ s.
:param Optional[bool] eq: If ``True`` or ``None`` (default), add ``__eq__``
    and ``__ne__`` methods that check two instances for equality.

    They compare the instances as if they were tuples of their ``attrs``
    attributes if and only if the types of both classes are *identical*!
:param Optional[bool] order: If ``True``, add ``__lt__``, ``__le__``,
    ``__gt__``, and ``__ge__`` methods that behave like *eq* above and
    allow instances to be ordered. If ``None`` (default) mirror value of
    *eq*.
:param Optional[bool] cmp: Setting *cmp* is equivalent to setting *eq*
    and *order* to the same value. Must not be mixed with *eq* or *order*.
:param Optional[bool] hash: If ``None`` (default), the ``__hash__`` method
    is generated according how *eq* and *frozen* are set.

    1. If *both* are True, ``attrs`` will generate a ``__hash__`` for you.
    2. If *eq* is True and *frozen* is False, ``__hash__`` will be set to
       None, marking it unhashable (which it is).
    3. If *eq* is False, ``__hash__`` will be left untouched meaning the
       ``__hash__`` method of the base class will be used (if base class is
       ``object``, this means it will fall back to id-based hashing.).

    Although not recommended, you can decide for yourself and force
    ``attrs`` to create one (e.g. if the class is immutable even though you
    didn't freeze it programmatically) by passing ``True`` or not.  Both of
    these cases are rather special and should be used carefully.

    See our documentation on `hashing`, Python's documentation on
    `object.__hash__`, and the `GitHub issue that led to the default \
    behavior <https://github.com/python-attrs/attrs/issues/136>`_ for more
    details.
:param bool init: Create a ``__init__`` method that initializes the
    ``attrs`` attributes. Leading underscores are stripped for the argument
    name. If a ``__attrs_pre_init__`` method exists on the class, it will
    be called before the class is initialized. If a ``__attrs_post_init__``
    method exists on the class, it will be called after the class is fully
    initialized.

    If ``init`` is ``False``, an ``__attrs_init__`` method will be
    injected instead. This allows you to define a custom ``__init__``
    method that can do pre-init work such as ``super().__init__()``,
    and then call ``__attrs_init__()`` and ``__attrs_post_init__()``.
:param bool slots: Create a `slotted class <slotted classes>` that's more
    memory-efficient. Slotted classes are generally superior to the default
    dict classes, but have some gotchas you should know about, so we
    encourage you to read the `glossary entry <slotted classes>`.
:param bool frozen: Make instances immutable after initialization.  If
    someone attempts to modify a frozen instance,
    `attr.exceptions.FrozenInstanceError` is raised.

    .. note::

        1. This is achieved by installing a custom ``__setattr__`` method
           on your class, so you can't implement your own.

        2. True immutability is impossible in Python.

        3. This *does* have a minor a runtime performance `impact
           <how-frozen>` when initializing new instances.  In other words:
           ``__init__`` is slightly slower with ``frozen=True``.

        4. If a class is frozen, you cannot modify ``self`` in
           ``__attrs_post_init__`` or a self-written ``__init__``. You can
           circumvent that limitation by using
           ``object.__setattr__(self, "attribute_name", value)``.

        5. Subclasses of a frozen class are frozen too.

:param bool weakref_slot: Make instances weak-referenceable.  This has no
    effect unless ``slots`` is also enabled.
:param bool auto_attribs: If ``True``, collect :pep:`526`-annotated
    attributes (Python 3.6 and later only) from the class body.

    In this case, you **must** annotate every field.  If ``attrs``
    encounters a field that is set to an `attr.ib` but lacks a type
    annotation, an `attr.exceptions.UnannotatedAttributeError` is
    raised.  Use ``field_name: typing.Any = attr.ib(...)`` if you don't
    want to set a type.

    If you assign a value to those attributes (e.g. ``x: int = 42``), that
    value becomes the default value like if it were passed using
    ``attr.ib(default=42)``.  Passing an instance of `attrs.Factory` also
    works as expected in most cases (see warning below).

    Attributes annotated as `typing.ClassVar`, and attributes that are
    neither annotated nor set to an `attr.ib` are **ignored**.

    .. warning::
       For features that use the attribute name to create decorators (e.g.
       `validators <validators>`), you still *must* assign `attr.ib` to
       them. Otherwise Python will either not find the name or try to use
       the default value to call e.g. ``validator`` on it.

       These errors can be quite confusing and probably the most common bug
       report on our bug tracker.

:param bool kw_only: Make all attributes keyword-only (Python 3+)
    in the generated ``__init__`` (if ``init`` is ``False``, this
    parameter is ignored).
:param bool cache_hash: Ensure that the object's hash code is computed
    only once and stored on the object.  If this is set to ``True``,
    hashing must be either explicitly or implicitly enabled for this
    class.  If the hash code is cached, avoid any reassignments of
    fields involved in hash code computation or mutations of the objects
    those fields point to after object creation.  If such changes occur,
    the behavior of the object's hash code is undefined.
:param bool auto_exc: If the class subclasses `BaseException`
    (which implicitly includes any subclass of any exception), the
    following happens to behave like a well-behaved Python exceptions
    class:

    - the values for *eq*, *order*, and *hash* are ignored and the
      instances compare and hash by the instance's ids (N.B. ``attrs`` will
      *not* remove existing implementations of ``__hash__`` or the equality
      methods. It just won't add own ones.),
    - all attributes that are either passed into ``__init__`` or have a
      default value are additionally available as a tuple in the ``args``
      attribute,
    - the value of *str* is ignored leaving ``__str__`` to base classes.
:param bool collect_by_mro: Setting this to `True` fixes the way ``attrs``
   collects attributes from base classes.  The default behavior is
   incorrect in certain cases of multiple inheritance.  It should be on by
   default but is kept off for backward-compatibility.

   See issue `#428 <https://github.com/python-attrs/attrs/issues/428>`_ for
   more details.

:param Optional[bool] getstate_setstate:
   .. note::
      This is usually only interesting for slotted classes and you should
      probably just set *auto_detect* to `True`.

   If `True`, ``__getstate__`` and
   ``__setstate__`` are generated and attached to the class. This is
   necessary for slotted classes to be pickleable. If left `None`, it's
   `True` by default for slotted classes and ``False`` for dict classes.

   If *auto_detect* is `True`, and *getstate_setstate* is left `None`,
   and **either** ``__getstate__`` or ``__setstate__`` is detected directly
   on the class (i.e. not inherited), it is set to `False` (this is usually
   what you want).

:param on_setattr: A callable that is run whenever the user attempts to set
    an attribute (either by assignment like ``i.x = 42`` or by using
    `setattr` like ``setattr(i, "x", 42)``). It receives the same arguments
    as validators: the instance, the attribute that is being modified, and
    the new value.

    If no exception is raised, the attribute is set to the return value of
    the callable.

    If a list of callables is passed, they're automatically wrapped in an
    `attrs.setters.pipe`.
:type on_setattr: `callable`, or a list of callables, or `None`, or
    `attrs.setters.NO_OP`

:param Optional[callable] field_transformer:
    A function that is called with the original class object and all
    fields right before ``attrs`` finalizes the class.  You can use
    this, e.g., to automatically add converters or validators to
    fields based on their types.  See `transform-fields` for more details.

:param bool match_args:
    If `True` (default), set ``__match_args__`` on the class to support
    :pep:`634` (Structural Pattern Matching). It is a tuple of all
    non-keyword-only ``__init__`` parameter names on Python 3.10 and later.
    Ignored on older Python versions.

.. versionadded:: 16.0.0 *slots*
.. versionadded:: 16.1.0 *frozen*
.. versionadded:: 16.3.0 *str*
.. versionadded:: 16.3.0 Support for ``__attrs_post_init__``.
.. versionchanged:: 17.1.0
   *hash* supports ``None`` as value which is also the default now.
.. versionadded:: 17.3.0 *auto_attribs*
.. versionchanged:: 18.1.0
   If *these* is passed, no attributes are deleted from the class body.
.. versionchanged:: 18.1.0 If *these* is ordered, the order is retained.
.. versionadded:: 18.2.0 *weakref_slot*
.. deprecated:: 18.2.0
   ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__`` now raise a
   `DeprecationWarning` if the classes compared are subclasses of
   each other. ``__eq`` and ``__ne__`` never tried to compared subclasses
   to each other.
.. versionchanged:: 19.2.0
   ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__`` now do not consider
   subclasses comparable anymore.
.. versionadded:: 18.2.0 *kw_only*
.. versionadded:: 18.2.0 *cache_hash*
.. versionadded:: 19.1.0 *auto_exc*
.. deprecated:: 19.2.0 *cmp* Removal on or after 2021-06-01.
.. versionadded:: 19.2.0 *eq* and *order*
.. versionadded:: 20.1.0 *auto_detect*
.. versionadded:: 20.1.0 *collect_by_mro*
.. versionadded:: 20.1.0 *getstate_setstate*
.. versionadded:: 20.1.0 *on_setattr*
.. versionadded:: 20.3.0 *field_transformer*
.. versionchanged:: 21.1.0
   ``init=False`` injects ``__attrs_init__``
.. versionchanged:: 21.1.0 Support for ``__attrs_pre_init__``
.. versionchanged:: 21.1.0 *cmp* undeprecated
.. versionadded:: 21.3.0 *match_args*
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