toJson method
Implementation
Map<String, Object> toJson() {
Map<String, Object> ret = {
'campaignId': campaignId,
'variationGroupId': variationGroupId,
'variationId': variationId,
'isReference': isReference,
'key': key
};
//Secure before adding the nullable
if (value != null) ret['value'] = value;
return ret;
}