public function normalizeValue($value)
	{
		$className  = $this->getFilterClassName();
		if ($value instanceof $className)
		{
			return $value;
		}

		if (!is_callable($value))
		{
			throw new InvalidArgumentException('Filter ' . var_export($value, true) . ' is neither callable nor an instance of ' . $className);
		}

		return new $className($value);
	}