sftp from an ssh connection?

[Paul]

I've seen a few posts in this list about getting an SSH connection
(with the net-ssh gem) and then using it to do sftp by calling .sftp
on the session object. This is exactly what I would like to do
(rather that start with sftp), but it looks like the "sftp" method on
the session object is not documented. I'm looking here:
http://net-ssh.rubyforge.org/ssh/v2/api/classes/Net/SSH/Connection/Session.html

Is it just an oversight in the documentation, or is it documented
somewhere else?

Thanks,
--Paul