code: function RuleTypeToRule(rule) {
          if (rule instanceof Rule)
              return rule;
          if (typeof (rule) === "string")
              return text(rule);
          if (typeof (rule) === "boolean")
              return rule ? Myna.truePredicate : Myna.falsePredicate;
          throw new Error("Invalid rule type: " + rule);
      }
docs: Given a RuleType returns an instance of a Rule.