function onDrain() {
			/*
			* [ANSI escape sequences][1]:
			*
			* -   `\u001b`: ESC, the escape character
			* -   `[1T`: scroll down one line
			* -   `[1G`: move the cursor to the beginning of the line
			*
			* [1]: https://en.wikipedia.org/wiki/ANSI_escape_code
			*/
			var str = '\u001b[1T\u001b[1G';
			pres._repl._ostream.write( str );
		}
Callback invoked upon a `drain` event.

@private