feat: Adds the Bound<'_, PyMappingProxy> type (#4644)

* Mappingproxy (#1)

Adds in the MappingProxy type.

* Move over from `iter` to `try_iter`.

* Added lifetime to `try_iter`, preventing need to clone when iterating.

* Remove unneccessary borrow.

* Add newsfragment

* Newline to newsfragment.

* Remove  explicit lifetime,

* Review comments (#2)

* Addressing more comments
* Remove extract_bound.
* Remove extract methods.

* Update comments for list return type.

---------

Co-authored-by: Kevin Matlock <[email protected]>

newsfragments/4644.added.md

@@ -0,0 +1 @@
+New `PyMappingProxy` struct corresponing to the `mappingproxy` class in Python. 

src/prelude.rs

@@ -38,6 +38,7 @@ pub use crate::types::float::PyFloatMethods;
 pub use crate::types::frozenset::PyFrozenSetMethods;
 pub use crate::types::list::PyListMethods;
 pub use crate::types::mapping::PyMappingMethods;
+pub use crate::types::mappingproxy::PyMappingProxyMethods;
 pub use crate::types::module::PyModuleMethods;
 pub use crate::types::sequence::PySequenceMethods;
 pub use crate::types::set::PySetMethods;

src/sealed.rs

@@ -1,7 +1,7 @@
 use crate::types::{
     PyBool, PyByteArray, PyBytes, PyCapsule, PyComplex, PyDict, PyFloat, PyFrozenSet, PyList,
-    PyMapping, PyModule, PySequence, PySet, PySlice, PyString, PyTraceback, PyTuple, PyType,
-    PyWeakref, PyWeakrefProxy, PyWeakrefReference,
+    PyMapping, PyMappingProxy, PyModule, PySequence, PySet, PySlice, PyString, PyTraceback,
+    PyTuple, PyType, PyWeakref, PyWeakrefProxy, PyWeakrefReference,
 };
 use crate::{ffi, Bound, PyAny, PyResult};
 
@@ -33,6 +33,7 @@ impl Sealed for Bound<'_, PyFloat> {}
 impl Sealed for Bound<'_, PyFrozenSet> {}
 impl Sealed for Bound<'_, PyList> {}
 impl Sealed for Bound<'_, PyMapping> {}
+impl Sealed for Bound<'_, PyMappingProxy> {}
 impl Sealed for Bound<'_, PyModule> {}
 impl Sealed for Bound<'_, PySequence> {}
 impl Sealed for Bound<'_, PySet> {}