toJson method
Implementation
core.Map<core.String, core.dynamic> toJson() => {
if (contactGroups != null) 'contactGroups': contactGroups!,
if (nextPageToken != null) 'nextPageToken': nextPageToken!,
if (nextSyncToken != null) 'nextSyncToken': nextSyncToken!,
if (totalItems != null) 'totalItems': totalItems!,
};