public function configKey($keyname, $option = null, $value = null)
    {
        if ($option === null) {
            $default = $this->_config;
            $local = isset($this->_keyConfig[$keyname]) ? $this->_keyConfig[$keyname] : [];

            return $local + $default;
        }
        if (!is_array($option)) {
            $option = [$option => $value];
        }
        $this->_keyConfig[$keyname] = $option;

        return null;
    }