toJson method
Implementation
core.Map<core.String, core.dynamic> toJson() => {
if (href != null) 'href': href!,
if (hreflang != null) 'hreflang': hreflang!,
if (media != null) 'media': media!,
if (rel != null) 'rel': rel!,
if (title != null) 'title': title!,
if (type != null) 'type': type!,
if (value != null) 'value': value!,
};