code: function _getRule(attribute, rules) {
      rules = rules || [];
  
      if ( ! rules[attribute]) {
        return;
      }
  
      for(var i in rules[attribute]) {
        var value = rules[attribute][i];
        parsedRule = _parseRule(rule);
  
        if (in_array(parsedRule.rule, rules))
          return [parsedRule.rule, parsedRule.parameters];
      }
    }
docs: get rule and parameters of a rules
  
  @param {String}       attribute
  @param {String|array} rules
  
  @return {Array|null}