public function removeValidationRules($field = null, array $rules = array()) {
        if (!$this->_validationLoaded) $this->_loadValidation();
        if (empty($rules) && is_string($field)) {
            unset($this->_validationRules[$this->getField($field)]);
        } elseif (empty($rules) && is_null($field)) {
            $this->_validationRules = array();
        } elseif (is_array($rules) && !empty($rules) && is_string($field)) {
            $field = $this->getField($field);
            foreach ($rules as $name) {
                unset($this->_validationRules[$field][$name]);
            }
        }
    }