Update

Author: vstinner

peps/pep-0782.rst

@@ -143,6 +143,9 @@ Getters
 
    Get the writer data.
 
+   The pointer is valid until :c:func:`PyBytesWriter_Finish` or
+   :c:func:`PyBytesWriter_Discard` is called on *writer*.
+
 Low-level API
 ^^^^^^^^^^^^^
 
@@ -282,6 +285,9 @@ used. It avoids having to resize a :class:`bytes` object which is
 inefficient. At the end, :c:func:`PyBytesWriter_Finish` creates the
 :class:`bytes` object from this small buffer.
 
+A free list is used to reduce the cost of allocating a
+:c:type:`PyBytesWriter` on the heap memory.
+
 
 Backwards Compatibility
 =======================