def open_sftp_client(self):
return SFTPClient.from_transport(self)<EOL>
Create an SFTP client channel from an open transport.  On success,
an SFTP session will be opened with the remote host, and a new
SFTPClient object will be returned.

@return: a new L{SFTPClient} object, referring to an sftp session
    (channel) across this transport
@rtype: L{SFTPClient}