code: def open(path, mode='r', host=None, user=None, port=DEFAULT_PORT):
      
      if not host:
          raise ValueError('you must specify the host to connect to')
      if not user:
          user = getpass.getuser()
      conn = _connect(host, user, port)
      sftp_client = conn.get_transport().open_sftp_client()
      return sftp_client.open(path, mode)
docs: Open a file on a remote machine over SSH.
  
      Expects authentication to be already set up via existing keys on the local machine.
  
      Parameters
      ----------
      path: str
          The path to the file to open on the remote machine.
      mode: str, optional
          The mode to use for opening the file.
      host: str, optional
          The hostname of the remote machine.  May not be None.
      user: str, optional
          The username to use to login to the remote machine.
          If None, defaults to the name of the current user.
      port: int, optional
          The port to connect to.
  
      Returns
      -------
      A file-like object.
  
      Important
      ---------
      If you specify a previously unseen host, then its host key will be added to
      the local ~/.ssh/known_hosts *automatically*.