toJson method
Implementation
core.Map<core.String, core.dynamic> toJson() => {
if (author != null) 'author': author!,
if (content != null) 'content': content!,
if (date != null) 'date': date!,
if (fullTextUrl != null) 'fullTextUrl': fullTextUrl!,
if (kind != null) 'kind': kind!,
if (rating != null) 'rating': rating!,
if (source != null) 'source': source!,
if (title != null) 'title': title!,
if (type != null) 'type': type!,
if (volumeId != null) 'volumeId': volumeId!,
};