This class implements an interface on top of a low-level SSL object as
implemented by OpenSSL. This object captures the state of an SSL connection
but does not provide any network IO itself. IO needs to be performed
through separate "BIO" objects which are OpenSSL's IO abstraction layer.
This class does not have a public constructor. Instances are returned by
``SSLContext.wrap_bio``. This class is typically used by framework authors
that want to implement asynchronous IO for SSL through memory buffers.
When compared to ``SSLSocket``, this object lacks the following features:
* Any form of network IO, including methods such as ``recv`` and ``send``.
* The ``do_handshake_on_connect`` and ``suppress_ragged_eofs`` machinery.