with manager.connect(host="*the IP adress*", port=*the port*, timeout=None, username="*user*", password="*pwd*") as m:
    c = m.get_config(source='running').data_xml
    with open("%s.xml" % host, 'w') as f:
        f.write(c)

File "<stdin>", line 1, in <module>
  File "/home/sisc/.local/lib/python2.7/site-packages/ncclient/manager.py", line 177, in connect
    return connect_ssh(*args, **kwds)
  File "/home/sisc/.local/lib/python2.7/site-packages/ncclient/manager.py", line 143, in connect_ssh
    session.connect(*args, **kwds)
  File "/home/sisc/.local/lib/python2.7/site-packages/ncclient/transport/ssh.py", line 481, in connect
    raise SSHUnknownHostError(known_hosts_lookup, fingerprint)
ncclient.transport.errors.SSHUnknownHostError: Unknown host key [e3:8d:35:a9:43:f9:3c:8a:f4:d3:88:5b:a9:36:93:59] for [[192.168.56.2]:1831]