code: function Rule(regexp) {
    this.regexp = regexp;
    var self = this;
    // proxy accumulators methods
    Object.keys(Rule.accumulators).forEach(function(name) {
      self[name] = function() {
        LOG("building rule:", regexp, "->", name);
        self.methodName = name;
        self.accumulatorParams = arguments;
        self.accumulatorBuilder = Rule.accumulators[name];
        return self;
      };
    });
  }
docs: regexp: a regular expression which a PDF item's text must match in order to execute that rule.
  => a Rule object exposes "accumulators": methods that defines the data extraction strategy of a rule.