cpython/Include/cpython/weakrefobject.h

#ifndef Py_CPYTHON_WEAKREFOBJECT_H
#  error "this header file must not be included directly"
#endif

/* PyWeakReference is the base struct for the Python ReferenceType, ProxyType,
 * and CallableProxyType.
 */
struct _PyWeakReference { … };

PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self);

#define _PyWeakref_CAST(op) …

Py_DEPRECATED(3.13) static inline PyObject* PyWeakref_GET_OBJECT(PyObject *ref_obj)
{ … }
#define PyWeakref_GET_OBJECT(ref) …