public function setClientConfig($id, ClientConfig $configSource) {
        $sources = $this->hasOption(self::OPTION_CONFIG_SOURCES)
            ? $this->getOption(self::OPTION_CONFIG_SOURCES)
            : array()
        ;
        $sources[$id] = $configSource;
        $this->setOption(self::OPTION_CONFIG_SOURCES, $sources);
    }