human
Complete the below
@documented_contextmanager
def remote_tunnel(remote_port, local_port=None, local_host='localhost', remote_bind_address='127.0.0.1'):

    ''''Create a tunnel forwarding a locally-visible port to the remote target.
    For example, you can let the remote host access a database that is
    installed on the client host::
    # Map localhost:6379 on the server to localhost:6379 on the client,
    # so that the remote \'redis-cli\' program ends up speaking to the local
    # redis-server.
    with remote_tunnel(6379):
    run("redis-cli -i")
    The database might be installed on a client only reachable from the client
    host (as opposed to *on* the client itself)::
    # Map localhost:6379 on the server to redis.internal:6379 on the client
    with remote_tunnel(6379, local_host="redis.internal")
    run("redis-cli -i")
    ``remote_tunnel`` accepts up to four arguments:
    * ``remote_port`` (mandatory) is the remote port to listen to.
    * ``local_port`` (optional) is the local port to connect to.
the default is
    the same port as the remote one.
    * ``local_host`` (optional) is the locally-reachable computer (DNS name or
    IP address) to connect to.
the default is ``localhost`` (that is, the
    same computer Fabric is running on).
    * ``remote_bind_address`` (optional) is the remote IP address to bind to
    for listening, on the current target. It should be an IP address assigned
    to an interface on the target (or a DNS name that resolves to such IP).
    You can use "0.0.0.0" to bind to all interfaces.
    .. note::
    By default, most SSH servers only allow remote tunnels to listen to the
    localhost interface (127.0.0.1). In these cases, `remote_bind_address`
    is ignored by the server, and the tunnel will listen only to 127.0.0.1.
    .. versionadded: 1.6'
    '''
 ... Write me a the Python code you requested?
assistant
#Here is the Python code you requested.
    if (local_port is None):
        local_port = remote_port
    sockets = []
    channels = []
    threads = []
    def accept(channel, (src_addr, src_port), (dest_addr, dest_port)):
        channels.append(channel)
        sock = socket.socket()
        sockets.append(sock)
        try:
            sock.connect((local_host, local_port))
        except Exception:
            print ('[%s]    rtunnel:    cannot    connect    to    %s:%d    (from    local)' % (env.host_string, local_host, local_port))
            channel.close()
            return
        print ('[%s]    rtunnel:    opened    reverse    tunnel:    %r    ->    %r    ->    %r' % (env.host_string, channel.origin_addr, channel.getpeername(), (local_host, local_port)))
        th = ThreadHandler('fwd', _forwarder, channel, sock)
        threads.append(th)
    transport = connections[env.host_string].get_transport()
    transport.request_port_forward(remote_bind_address, remote_port, handler=accept)
    try:
        (yield)
    finally:
        for (sock, chan, th) in zip(sockets, channels, threads):
            sock.close()
            chan.close()
            th.thread.join()
            th.raise_if_needed()
        transport.cancel_port_forward(remote_bind_address, remote_port)