bpo-37249: add declaration of _PyObject_GetMethod (GH-14015)

diff --git a/Include/cpython/object.h b/Include/cpython/object.h
index a65aaf6..fd4e771 100644
--- a/Include/cpython/object.h
+++ b/Include/cpython/object.h
@@ -318,6 +318,9 @@
 */
 PyAPI_FUNC(int) _PyObject_LookupAttr(PyObject *, PyObject *, PyObject **);
 PyAPI_FUNC(int) _PyObject_LookupAttrId(PyObject *, struct _Py_Identifier *, PyObject **);
+
+PyAPI_FUNC(int) _PyObject_GetMethod(PyObject *obj, PyObject *name, PyObject **method);
+
 PyAPI_FUNC(PyObject **) _PyObject_GetDictPtr(PyObject *);
 PyAPI_FUNC(PyObject *) _PyObject_NextNotImplemented(PyObject *);
 PyAPI_FUNC(void) PyObject_CallFinalizer(PyObject *);