public function source($filename = null)
    {
        if ($filename) {
            $this->source = $filename;

            return $this;
        }

        return $this->source ?? $this->config['source'];
    }
public function source($filename = null)
    {
        if ($filename) {
            $this->source = $filename;

            return $this;
        }

        return $this->source ?? $this->config['source'];
    }
{@inheritDoc}