Return ``True`` if *class* is a subclass (direct, indirect, or :term:`virtual
<abstract base class>`) of *classinfo*. A
class is considered a subclass of itself. *classinfo* may be a tuple of class
- objects or a :ref:`types-union`, in which case return ``True`` if *class* is a
+ objects (or recursively, other such tuples)
+ or a :ref:`types-union`, in which case return ``True`` if *class* is a
subclass of any entry in *classinfo*. In any other case, a :exc:`TypeError`
exception is raised.