I get error when doing Parser.stringify(ast)

[Tim Clemans]

var ast = Parser.parse("$select=date, type, magnitude&$where=magnitude > 3.0 and source = 'pr'&$group=type");
undefined
> Parser.stringify(ast)
TypeError: Parser.stringify is not a function
    at repl:1:8
    at REPLServer.defaultEval (repl.js:260:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:429:12)
    at emitOne (events.js:95:20)
    at REPLServer.emit (events.js:182:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
    at REPLServer.Interface._ttyWrite (readline.js:827:14)