public function exists($group, $namespace = null)
    {
        $key = $group.$namespace;

        // We'll first check to see if we have determined if this namespace and
        // group combination have been checked before. If they have, we will
        // just return the cached result so we don't have to hit the disk.
        if (isset($this->exists[$key])) {
            return $this->exists[$key];
        }

        $path = $this->getPath($namespace);

        // To check if a group exists, we will simply get the path based on the
        // namespace, and then check to see if this files exists within that
        // namespace. False is returned if no path exists for a namespace.
        if (is_null($path)) {
            return $this->exists[$key] = false;
        }

        $file = "{$path}/{$group}.php";

        // Finally, we can simply check if this file exists. We will also cache
        // the value in an array so we don't have to go through this process
        // again on subsequent checks for the existing of the config file.
        $exists = $this->files->exists($file);

        return $this->exists[$key] = $exists;
    }