How to use the datx.getRefId function in datx

Object.keys(refs).forEach((key) => {
    data.relationships = data.relationships || { };
    const refIds = getRefId(model, key);
    let rel: IDefinition|Array|undefined;
    if (refIds instanceof Array || isObservableArray(refIds)) {
      rel = (refIds as Array).map((id, index) => {
        const type = getModelType(model[key][index] ? model[key][index] : refs[key].model).toString();

        if (!type) {
          throw error(`The model type can't be retrieved for the reference ${key}`);
        }

        return { id, type };
      });
    } else {
      const type: string = getModelType(model[key] ? model[key] : refs[key].model).toString();

      if (!type) {
        throw error(`The model type can't be retrieved for the reference ${key}`);

export function saveRelationship(
  model: T,
  ref: string,
  options?: IRequestOptions,
): Promise {
  const collection = getModelCollection(model) as IJsonapiCollection;
  const link = getLink(model, ref, 'self');
  const href: string = typeof link === 'object' ? link.href : link;

  const ids = getRefId(model, ref);
  const type = getModelType(getModelMetaKey(model, 'refs')[ref].model);
  type ID = IDefinition|Array;
  const data: ID = mapItems(ids, (id) => ({ id, type })) as ID;

  return update(href, { data }, collection, options && options.headers)
    .then(handleResponse(model, ref));
}