code: def sshclient_from_instance(instance, ssh_key_file,
                              host_key_file='~/.ssh/known_hosts',
                              user_name='root', ssh_pwd=None):
      
      s = FakeServer(instance, ssh_key_file)
      return SSHClient(s, host_key_file, user_name, ssh_pwd)
docs: Create and return an SSHClient object given an
      instance object.
  
      :type instance: :class`boto.ec2.instance.Instance` object
      :param instance: The instance object.
  
      :type ssh_key_file: str
      :param ssh_key_file: A path to the private key file used
                           to log into instance.
  
      :type host_key_file: str
      :param host_key_file: A path to the known_hosts file used
                            by the SSH client.
                            Defaults to ~/.ssh/known_hosts
      :type user_name: str
      :param user_name: The username to use when logging into
                        the instance.  Defaults to root.
  
      :type ssh_pwd: str
      :param ssh_pwd: The passphrase, if any, associated with
                      private key.