bpo-39947: Add PyThreadState_GetFrame() function (GH-19092)

Add PyThreadState_GetFrame() function: get the current frame
of a Python thread state.
diff --git a/Doc/c-api/init.rst b/Doc/c-api/init.rst
index a4ec0e3..294c1b9 100644
--- a/Doc/c-api/init.rst
+++ b/Doc/c-api/init.rst
@@ -1072,6 +1072,18 @@
    to :c:func:`PyThreadState_Clear`.
 
 
+.. c:function:: PyFrameObject* PyThreadState_GetFrame(PyThreadState *tstate)
+
+   Get the current frame of the Python thread state *tstate*. It can be
+   ``NULL`` if no frame is currently executing.
+
+   See also :c:func:`PyEval_GetFrame`.
+
+   *tstate* must not be ``NULL``.
+
+   .. versionadded:: 3.9
+
+
 .. c:function:: PyInterpreterState* PyThreadState_GetInterpreter(PyThreadState *tstate)
 
    Get the interpreter of the Python thread state *tstate*.
diff --git a/Doc/c-api/reflection.rst b/Doc/c-api/reflection.rst
index 1d86de6..4d3d25e 100644
--- a/Doc/c-api/reflection.rst
+++ b/Doc/c-api/reflection.rst
@@ -5,29 +5,31 @@
 Reflection
 ==========
 
-.. c:function:: PyObject* PyEval_GetBuiltins()
+.. c:function:: PyObject* PyEval_GetBuiltins(void)
 
    Return a dictionary of the builtins in the current execution frame,
    or the interpreter of the thread state if no frame is currently executing.
 
 
-.. c:function:: PyObject* PyEval_GetLocals()
+.. c:function:: PyObject* PyEval_GetLocals(void)
 
    Return a dictionary of the local variables in the current execution frame,
    or ``NULL`` if no frame is currently executing.
 
 
-.. c:function:: PyObject* PyEval_GetGlobals()
+.. c:function:: PyObject* PyEval_GetGlobals(void)
 
    Return a dictionary of the global variables in the current execution frame,
    or ``NULL`` if no frame is currently executing.
 
 
-.. c:function:: PyFrameObject* PyEval_GetFrame()
+.. c:function:: PyFrameObject* PyEval_GetFrame(void)
 
    Return the current thread state's frame, which is ``NULL`` if no frame is
    currently executing.
 
+   See also :c:func:`PyThreadState_GetFrame`.
+
 
 .. c:function:: int PyFrame_GetLineNumber(PyFrameObject *frame)