def start_subsystem(self, name, transport, channel):
pass<EOL>
Process an ssh subsystem in server mode.  This method is called on a
new object (and in a new thread) for each subsystem request.  It is
assumed that all subsystem logic will take place here, and when the
subsystem is finished, this method will return.  After this method
returns, the channel is closed.

The combination of ``transport`` and ``channel`` are unique; this
handler corresponds to exactly one `.Channel` on one `.Transport`.

.. note::
    It is the responsibility of this method to exit if the underlying
    `.Transport` is closed.  This can be done by checking
    `.Transport.is_active` or noticing an EOF on the `.Channel`.  If
    this method loops forever without checking for this case, your
    Python interpreter may refuse to exit because this thread will
    still be running.

:param str name: name of the requested subsystem.
:param .Transport transport: the server-mode `.Transport`.
:param .Channel channel: the channel associated with this subsystem
    request.