public function writeInnerXml(\XMLWriter $xmlWriter)
    {
        Validate::notNull($xmlWriter, 'xmlWriter');
        if (!is_null($this->attributes)) {
            if (is_array($this->attributes)) {
                foreach ($this->attributes as $attributeName => $attributeValue) {
                    $xmlWriter->writeAttribute($attributeName, $attributeValue);
                }
            }
        }

        if (!is_null($this->author)) {
            Validate::isArray($this->author, Resources::AUTHOR);
            $this->writeArrayItem($xmlWriter, $this->author, Resources::AUTHOR);
        }

        if (!is_null($this->category)) {
            Validate::isArray($this->category, Resources::CATEGORY);
            $this->writeArrayItem(
                $xmlWriter,
                $this->category,
                Resources::CATEGORY
            );
        }

        if (!is_null($this->contributor)) {
            Validate::isArray($this->contributor, Resources::CONTRIBUTOR);
            $this->writeArrayItem(
                $xmlWriter,
                $this->contributor,
                Resources::CONTRIBUTOR
            );
        }

        if (!is_null($this->generator)) {
            $this->generator->writeXml($xmlWriter);
        }

        if (!is_null($this->icon)) {
            $xmlWriter->writeElementNS(
                'atom',
                'icon',
                Resources::ATOM_NAMESPACE,
                $this->icon
            );
        }

        $this->writeOptionalElementNS(
            $xmlWriter,
            'atom',
            'logo',
            Resources::ATOM_NAMESPACE,
            $this->logo
        );

        $this->writeOptionalElementNS(
            $xmlWriter,
            'atom',
            'id',
            Resources::ATOM_NAMESPACE,
            $this->id
        );

        if (!is_null($this->link)) {
            Validate::isArray($this->link, Resources::LINK);
            $this->writeArrayItem(
                $xmlWriter,
                $this->link,
                Resources::LINK
            );
        }

        $this->writeOptionalElementNS(
            $xmlWriter,
            'atom',
            'rights',
            Resources::ATOM_NAMESPACE,
            $this->rights
        );

        $this->writeOptionalElementNS(
            $xmlWriter,
            'atom',
            'subtitle',
            Resources::ATOM_NAMESPACE,
            $this->subtitle
        );

        $this->writeOptionalElementNS(
            $xmlWriter,
            'atom',
            'title',
            Resources::ATOM_NAMESPACE,
            $this->title
        );

        if (!is_null($this->updated)) {
            $xmlWriter->writeElementNS(
                'atom',
                'updated',
                Resources::ATOM_NAMESPACE,
                $this->updated->format(\DateTime::ATOM)
            );
        }
    }