inspect.classify_class_attrs ignores metaclass

Doc/library/inspect.rst

 :mod:`inspect` --- Inspect live objects
 =======================================
 
 .. module:: inspect
    :synopsis: Extract information and source code from live objects.
 .. moduleauthor:: Ka-Ping Yee <ping@lfw.org>
 .. sectionauthor:: Ka-Ping Yee <ping@lfw.org>
 
 **Source code:** :source:`Lib/inspect.py`
 
@@ skipping 155 matching lines @@
 
 
 .. function:: getmembers(object[, predicate])
 
    Return all the members of an object in a list of (name, value) pairs sorted by
    name.  If the optional *predicate* argument is supplied, only members for which
    the predicate returns a true value are included.
 
    .. note::
 
-      :func:`getmembers` does not return metaclass attributes when the argument
-      is a class (this behavior is inherited from the :func:`dir` function).
+      :func:`getmembers` will only return metaclass attributes when the
+      argument is a class and those attributes have been listed in a custom
+      :meth:`__dir__`.
 
 
 .. function:: getmoduleinfo(path)
 
    Returns a :term:`named tuple` ``ModuleInfo(name, suffix, mode, module_type)``
    of values that describe how Python will interpret the file identified by
    *path* if it is a module, or ``None`` if it would not be identified as a
    module.  In that tuple, *name* is the name of the module without the name of
    any enclosing package, *suffix* is the trailing part of the file name (which
    may not be a dot-delimited extension), *mode* is the :func:`open` mode that
@@ skipping 810 matching lines @@
    *generator* is not a Python generator object.
 
    .. impl-detail::
 
       This function relies on the generator exposing a Python stack frame
       for introspection, which isn't guaranteed to be the case in all
       implementations of Python. In such cases, this function will always
       return an empty dictionary.
 
    .. versionadded:: 3.3