public function dataSourceFilter($sourceIdent)
    {
        if (!is_string($sourceIdent)) {
            throw new InvalidArgumentException('Data source identifier must be a string');
        }

        $filters = array_merge($this->defaultDataSourceFilters(), $this->dataSourceFilters);

        if (isset($filters[$sourceIdent])) {
            return $filters[$sourceIdent];
        }

        return null;
    }