Here is a bytes type. It's very minimal but it's a start.

Include/bytesobject.h

@@ -0,0 +1,47 @@
+/* Bytes object interface */
+
+#ifndef Py_BYTESOBJECT_H
+#define Py_BYTESOBJECT_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdarg.h>
+
+/* Type PyBytesObject represents a mutable array of bytes.
+ * The Python API is that of a sequence;
+ * the bytes are mapped to ints in [0, 256).
+ * Bytes are not characters; they may be used to encode characters.
+ * The only way to go between bytes and str/unicode is via encoding
+ * and decoding.
+ * For the concenience of C programmers, the bytes type is considered
+ * to contain a char pointer, not an unsigned char pointer.
+ */
+
+/* Object layout */
+typedef struct {
+    PyObject_VAR_HEAD
+    char *ob_sval;
+} PyBytesObject;
+
+/* Type object */
+PyAPI_DATA(PyTypeObject) PyBytes_Type;
+
+/* Type check macros */
+#define PyBytes_Check(self) PyObject_TypeCheck(self, &PyBytes_Type)
+#define PyBytes_CheckExact(self) ((self)->ob_type == &PyBytes_Type)
+
+/* Direct API functions */
+PyAPI_FUNC(PyObject *) PyBytes_FromStringAndSize(const char *, Py_ssize_t);
+PyAPI_FUNC(Py_ssize_t) PyBytes_Size(PyObject *);
+PyAPI_FUNC(char *) PyBytes_AsString(PyObject *);
+PyAPI_FUNC(int) PyBytes_Resize(PyObject *, Py_ssize_t);
+
+/* Macros, trading safety for speed */
+#define PyBytes_AS_STRING(self) (((PyBytesObject *)(self))->ob_sval)
+#define PyBytes_GET_SIZE(self)  (((PyBytesObject *)(self))->ob_size)
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_BYTESOBJECT_H */