toJson method
Implementation
@override
Map<String, dynamic> toJson() => {
'type': 'string',
if (title != null) 'title': title,
if (description != null) 'description': description,
if (defaultValue != null) 'default': defaultValue,
if (format != null) 'format': format,
if (minLength != null) 'minLength': minLength,
if (maxLength != null) 'maxLength': maxLength,
};