code: function (tuple) {
  		var line = this.readLine();
  		var colon = line.indexOf(":");
  		if (colon == -1) throw "Invalid line: " + line;
  		var i = 0, lastMatch = colon + 1;
  		for (; i < 3; i++) {
  			var comma = line.indexOf(",", lastMatch);
  			if (comma == -1) break;
  			tuple[i] = this.trim(line.substr(lastMatch, comma - lastMatch));
  			lastMatch = comma + 1;
  		}
  		tuple[i] = this.trim(line.substring(lastMatch));
  		return i + 1;
  	}
docs: Returns the number of tuple values read (1, 2 or 4).