private function _checkConfig($config = null)
    {
        if ($config === null) {
            $config = $this->config;
        }
        if (!($config instanceof ArrayAccess)
            && !is_array($config)
        ) {
            throw new Klarna_IncompleteConfigurationException;
        }
    }
private function _checkConfig($config = null)
    {
        if ($config === null) {
            $config = $this->config;
        }
        if (!($config instanceof ArrayAccess)
            && !is_array($config)
        ) {
            throw new Klarna_IncompleteConfigurationException;
        }
    }
private function _checkConfig ( $ config = null ) { if ( $ config === null ) { $ config = $ this -> config ; } if ( ! ( $ config instanceof ArrayAccess ) && ! is_array ( $ config ) ) { throw new Klarna_IncompleteConfigurationException ; } }
Ensure the configuration is of the correct type.

@param array|ArrayAccess|null $config an optional config to validate

@return void
Ensure the configuration is of the correct type .