code: function(model, attr, value, computed) {
        // Reduces the array of validators to an error message by
        // applying all the validators and returning the first error
        // message, if any.
        var hasErrors, subAttr, result,
          validators = getValidators(model, attr);
        subAttr = generateSubAttributes(attr, model);
        result = validateWithOpenArrayHelper(model, subAttr, value, computed, validators, 0);
        if (_.isArray(result)) {
          hasErrors = _.reduce(_.flatten(result), function(memo, val) {
            return memo || val;
          }, false);
          if (!hasErrors) {
            return '';
          }
        }
        return result;
      }
docs: Validates an attribute against all validators defined for that attribute. If one or more errors are found, the first error message is returned. If the attribute is valid, an empty string is returned.