code: function verifyModifier(predicate, defaultMessage) {
          return function () {
            var message;
            if (predicate.apply(null, arguments) === false) {
              message = arguments[arguments.length - 1];
              throw new Error(check.unemptyString(message) ? message : defaultMessage);
            }
          };
        }
docs: Public modifier `verify`.
  
  Throws if `predicate` returns `false`.
  copied from check-types.js