public function getProperty($nameOrProperty): PhpProperty {
		if ($nameOrProperty instanceof PhpProperty) {
			$nameOrProperty = $nameOrProperty->getName();
		}

		if (!$this->properties->has($nameOrProperty)) {
			throw new \InvalidArgumentException(sprintf('The property "%s" does not exist.', $nameOrProperty));
		}

		return $this->properties->get($nameOrProperty);
	}