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venv/lib/python3.12/site-packages/bidict/_abc.py

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+# Copyright 2009-2024 Joshua Bronson. All rights reserved.
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+#                             * Code review nav *
+#                        (see comments in __init__.py)
+# ============================================================================
+# ← Prev: __init__.py          Current: _abc.py               Next: _base.py →
+# ============================================================================
+
+
+"""Provide the :class:`BidirectionalMapping` abstract base class."""
+
+from __future__ import annotations
+
+import typing as t
+from abc import abstractmethod
+
+from ._typing import KT
+from ._typing import VT
+
+
+class BidirectionalMapping(t.Mapping[KT, VT]):
+    """Abstract base class for bidirectional mapping types.
+
+    Extends :class:`collections.abc.Mapping` primarily by adding the
+    (abstract) :attr:`inverse` property,
+    which implementers of :class:`BidirectionalMapping`
+    should override to return a reference to the inverse
+    :class:`BidirectionalMapping` instance.
+    """
+
+    __slots__ = ()
+
+    @property
+    @abstractmethod
+    def inverse(self) -> BidirectionalMapping[VT, KT]:
+        """The inverse of this bidirectional mapping instance.
+
+        *See also* :attr:`bidict.BidictBase.inverse`, :attr:`bidict.BidictBase.inv`
+
+        :raises NotImplementedError: Meant to be overridden in subclasses.
+        """
+        # The @abstractmethod decorator prevents subclasses from being instantiated unless they
+        # override this method. But an overriding implementation may merely return super().inverse,
+        # in which case this implementation is used. Raise NotImplementedError to indicate that
+        # subclasses must actually provide their own implementation.
+        raise NotImplementedError
+
+    def __inverted__(self) -> t.Iterator[tuple[VT, KT]]:
+        """Get an iterator over the items in :attr:`inverse`.
+
+        This is functionally equivalent to iterating over the items in the
+        forward mapping and inverting each one on the fly, but this provides a
+        more efficient implementation: Assuming the already-inverted items
+        are stored in :attr:`inverse`, just return an iterator over them directly.
+
+        Providing this default implementation enables external functions,
+        particularly :func:`~bidict.inverted`, to use this optimized
+        implementation when available, instead of having to invert on the fly.
+
+        *See also* :func:`bidict.inverted`
+        """
+        return iter(self.inverse.items())
+
+
+class MutableBidirectionalMapping(BidirectionalMapping[KT, VT], t.MutableMapping[KT, VT]):
+    """Abstract base class for mutable bidirectional mapping types."""
+
+    __slots__ = ()
+
+
+#                             * Code review nav *
+# ============================================================================
+# ← Prev: __init__.py          Current: _abc.py               Next: _base.py →
+# ============================================================================