Wrapper Class for Paramiko

I used paramiko for a project a while ago and wrote the following, called sftp_wrapper.py, to help with things:

'''
sftp_wrapper.py is a wrapper class for the sftp portion of the 
paramiko library.
'''

import paramiko

class Session(object):
    def __init__(self, hostname, username, password):
        self.tunnel = paramiko.Transport((hostname, 22))
        hostkeys = paramiko.util.load_host_keys('known_hosts')
        hostkey = hostkeys[hostname]['ssh-rsa']
        self.tunnel.connect(username=username, password=password,
            hostkey=hostkey)
        self.sftp = paramiko.SFTPClient.from_transport(self.tunnel)

    def open(self, filename, mode='r'):
        return self.sftp.open(filename, mode=mode)

    def chdir(self, dir):
        self.sftp.chdir(dir)

    def get(self, remote, local=None):
        if not local:
            local = remote
        self.sftp.get(remote, local)

    def put(self, local, remote=None):
        if not remote:
            remote = local
        self.sftp.put(local, remote)

    def listdir(self, remote):
        return self.sftp.listdir(remote)

    def remove(self, remote):
        self.sftp.remove(remote)

    def close(self):
        self.tunnel.close()