Add macro to assert critical section is held

Author: DinoV

Include/internal/pycore_critical_section.h

@@ -104,12 +104,14 @@ extern "C" {
 # define Py_END_CRITICAL_SECTION2()                                     \
         _PyCriticalSection2_End(&_cs2);                                 \
     }
+#define  _Py_CRITICAL_SECTION_ASSERT_HELD(op) assert(PyMutex_IsLocked(&_PyObject_CAST(op)->ob_mutex))
 #else  /* !Py_GIL_DISABLED */
 // The critical section APIs are no-ops with the GIL.
 # define Py_BEGIN_CRITICAL_SECTION(op)
 # define Py_END_CRITICAL_SECTION()
 # define Py_BEGIN_CRITICAL_SECTION2(a, b)
 # define Py_END_CRITICAL_SECTION2()
+#define  _Py_CRITICAL_SECTION_ASSERT_HELD(op)
 #endif  /* !Py_GIL_DISABLED */
 
 typedef struct {