public function isLoaded($className)
    {
        $this->typeCheck->isLoaded(func_get_args());

        return array_key_exists($className, $this->extensions);
    }
public function isLoaded($className)
    {
        $this->typeCheck->isLoaded(func_get_args());

        return array_key_exists($className, $this->extensions);
    }
@param string $className The name of the extension class.

@return boolean