protected function checkOverrider($namespace)
    {
        if ($this->allowOverride && isset($this->overrides[$namespace])) {
            $oldNamespace = $namespace;

            $namespace = $this->overrides[$namespace]['overrider'];
            $this->classExists($namespace);

            if ($this->overrides[$oldNamespace]['only_once']) {
                $this->unsetOverrider($oldNamespace);
            }
        }

        return $namespace;
    }