code: function UI( opt ) {
    // Instantiate the Readline interface
    // @Note: Don't reassign if already present (allow test to override the Stream)
    this.rl || (this.rl = readlineFacade.createInterface());
    this.rl.resume();
  
    this.onForceClose = this.onForceClose.bind(this);
    this.onKeypress = this.onKeypress.bind(this);
  
    // Make sure new prompt start on a newline when closing
    this.rl.on( "SIGINT", this.onForceClose );
    process.on( "exit", this.onForceClose );
  
    // Propagate keypress events directly on the readline
    process.stdin.addListener( "keypress", this.onKeypress );
  }
docs: Constructor