code: function (expression, types) {
          var args = types.split(" | "),
              i, len, found = false;
  
          for (i=0, len=args.length; i < len && !found && expression.hasNext(); i++) {
              found = this.isType(expression, args[i]);
          }
  
          return found;
      }
docs: Determines if the next part(s) of the given expression
  are any of the given types.