cpython/Include/cpython/bytesobject.h

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

PyBytesObject;

PyAPI_FUNC(int) _PyBytes_Resize(PyObject **, Py_ssize_t);

/* Macros and static inline functions, trading safety for speed */
#define _PyBytes_CAST(op) …

static inline char* PyBytes_AS_STRING(PyObject *op)
{ … }
#define PyBytes_AS_STRING(op) …

static inline Py_ssize_t PyBytes_GET_SIZE(PyObject *op) { … }
#define PyBytes_GET_SIZE(self) …

PyAPI_FUNC(PyObject*) PyBytes_Join(PyObject *sep, PyObject *iterable);

// Alias kept for backward compatibility
#define _PyBytes_Join …