gh-108314: Add PyDict_ContainsString() function (#108323)

Doc/c-api/dict.rst

@@ -55,6 +55,15 @@ Dictionary Objects
    This is equivalent to the Python expression ``key in p``.
 
 
+.. c:function:: int PyDict_ContainsString(PyObject *p, const char *key)
+
+   This is the same as :c:func:`PyDict_Contains`, but *key* is specified as a
+   :c:expr:`const char*` UTF-8 encoded bytes string, rather than a
+   :c:expr:`PyObject*`.
+
+   .. versionadded:: 3.13
+
+
 .. c:function:: PyObject* PyDict_Copy(PyObject *p)
 
    Return a new dictionary that contains the same key-value pairs as *p*.
@@ -73,7 +82,7 @@ Dictionary Objects
    .. index:: single: PyUnicode_FromString()
 
    Insert *val* into the dictionary *p* using *key* as a key. *key* should
-   be a :c:expr:`const char*`.  The key object is created using
+   be a :c:expr:`const char*` UTF-8 encoded bytes string.  The key object is created using
    ``PyUnicode_FromString(key)``.  Return ``0`` on success or ``-1`` on
    failure.  This function *does not* steal a reference to *val*.
 
@@ -88,7 +97,8 @@ Dictionary Objects
 
 .. c:function:: int PyDict_DelItemString(PyObject *p, const char *key)
 
-   Remove the entry in dictionary *p* which has a key specified by the string *key*.
+   Remove the entry in dictionary *p* which has a key specified by the UTF-8
+   encoded bytes string *key*.
    If *key* is not in the dictionary, :exc:`KeyError` is raised.
    Return ``0`` on success or ``-1`` on failure.
 
@@ -136,7 +146,8 @@ Dictionary Objects
 .. c:function:: PyObject* PyDict_GetItemString(PyObject *p, const char *key)
 
    This is the same as :c:func:`PyDict_GetItem`, but *key* is specified as a
-   :c:expr:`const char*`, rather than a :c:expr:`PyObject*`.
+   :c:expr:`const char*` UTF-8 encoded bytes string, rather than a
+   :c:expr:`PyObject*`.
 
    .. note::
 
@@ -150,7 +161,8 @@ Dictionary Objects
 .. c:function:: int PyDict_GetItemStringRef(PyObject *p, const char *key, PyObject **result)
 
    Similar than :c:func:`PyDict_GetItemRef`, but *key* is specified as a
-   :c:expr:`const char*`, rather than a :c:expr:`PyObject*`.
+   :c:expr:`const char*` UTF-8 encoded bytes string, rather than a
+   :c:expr:`PyObject*`.
 
    .. versionadded:: 3.13