Improve the description of the open function

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

Author: furkanonder

Doc/library/shelve.rst

@@ -44,13 +44,18 @@ lots of shared  sub-objects.  The keys are ordinary strings.
 
    By default, :mod:`shelve` uses :func:`pickle.dumps` and :func:`pickle.loads`
    for serializing and deserializing. This can be changed by supplying
-   *serializer* and *deserializer*, respectively. The *serializer* argument
-   should be a function that takes an object and the *protocol* argument passed
-   to the open function and returns its representation as a
-   :term:`bytes-like object`; *protocol* argument that may be ignored by the
-   function. *deserializer* should be a function that takes :class:`bytes` and
-   returns the corresponding object. If one of these is given, the other must
-   be given as well. Otherwise :mod:`shelve` will raise a :exc:`ShelveError`.
+   *serializer* and *deserializer*, respectively.
+
+   The *serializer* argument must be a callable which takes an object ``obj``
+   and the *protocol* as inputs and returns the representation ``obj`` as a
+   :term:`bytes-like object`; the *protocol* value may be ignored by the
+   serializer.
+
+   The *deserializer* argument must be callable which takes a serialized object
+   given as a :class:`bytes` object and returns the corresponding object.
+
+   A :exc:`ShelveError` is raised if *serializer* is given but *deserializer*
+   is not, or vice-versa.
 
    .. versionchanged:: 3.10
       :const:`pickle.DEFAULT_PROTOCOL` is now used as the default pickle